Seiko has used many different materials for watch cases over the years. These greatly expanded in the late 70's and 80's when a range of different case materials were tested and various materials were employed to utilize their specific properties. The different materials used in the watch case construction are detailed in product catalogs and are often indicated on the case itself.

This listing was initially created from the 1991 Seiko JDM dealer catalog but additional items have been added. The abbreviation is the case material that is listed in the catalogs and the case back stamping is what is often but not always marked on the watch case back.

Here is an example of the case material codes from the 1991 Vol. 1 Catalog, e.g. SBBS018 has the case material code of THGMCETIHG, the SBBN001 has a code of TIHC.TI and the SSBT014 has TIHNT.TI.

The original 1991 listing from the JDM catalog can be downloaded from here - 1991 Seiko Case Codes JDM Catalog Vol1.pdf

See below for a table listing the various case material codes that have been used used.

Abbreviation Description Case Back Stamping
10KXS Case of 10K yellow gold with reinforced inner body with SS 10K BASE ST.STEEL ST.STEEL BACK
10KYS 10K yellow gold case, SS case back 10K ST.STEEL BACK
14K.GP 14K yellow gold case, GP case back 14KT BASE METAL BACK
14KCE Combined case with 14K yellow gold and ceramic 14KT + CERAMICS ST.STEEL BACK
14KXS Case of 14K yellow gold with reinforced inner body with SS 14K BASE ST.STEEL ST.STEEL BACK
14KYS 14K yellow gold case, SS case back 14K ST.STEEL BACK
18K 18K yellow gold case 18K (18KT)
18KWG 18K white gold case 18KT
18KYG 18K yellow gold case 18K (18KT)
AAPC All Aluminum Palladium Alloy AAPC
ABCRP Black chrome plated case. Back lid black chrome plating BASE METAL
ACRP Chrome plated case. Back cover chrome plating CRP
AGF All Gold Filled AGF
AGPRUP Ruthenium-plated on gold-plated case of the cast-in-tone. Back cover GPRUP BASE METAL
AHC All Hard Coat, case coated with hard titanium nitride. Back cover HC BASE METAL
AHGC Case coated with hard titanium nitride. (Surface hardness or resistance to small scratches, Hv = 1200) Back side HCC HGC
ALM Rigid light alloy ALM
ALSGP All Light SEIKO Gold Colour Plated case ALSGP
APDP Case and case back with applied palladium plating. PDP
ASG All SEIKO Gold Plated case SGP
ASGP Gold plating. Gold back plated SGP
ASILVER All Silver. SILVER 850 is difficult to tarnish (sulfide) uniquely developed by SEIKO, it is a hard finish or fine silver xxx SILVER or SILVER xxx
ASSGP Part of stainless steel plated with gold. Partially gold-plated back cover ST.STEEL+ BASE METAL
ATI All Titanium case. (Excellent corrosion resistance and light weight) Backside Titanium. TITANIUM
ATIHC Titanium case coated with hard titanium nitride. (Same for rear cover) (In addition to the features on the titanium side, it is strong in surface hardness or high scratch resistance. Hv = about 1200) TITANIUM
ATIHICDC All TI case with super hard coating TITANIUM
AWGF All White Gold Filled AWGF
AWGP All White Gold Plating AWGP
BCRP Black chrome plated side. Back SS BCRP ST.STEEL BACK
BCRP-PCD Case combining black chrome plating and plastic resin.  BASE METAL+ PLASTICS ST.STEEL BACK
BTIHC.MBTIHC All high intensity titanium TITANIUM
CE Ceramic Case (hard highly scratch resistant, Hv = 1500, no rusting, with a beautiful surface) ** CERAMICS ST.STEEL BACK
CEAC Case where the ceramic was coated with hard titanium nitride.  CERAMICS ST.STEEL BACK
CEHGC Part ceramic on which the coating of hard titanium nitride was applied.  CERAMICS ST.STEEL BACK
CRP Chrome plated case.  CRP ST.STEEL BACK
FRC Blowing fluorocarbon resin to the lower side of the coating.  BASE METAL ST.STEEL BACK
FRC.PCD Fused case combined resin coating and plastic resin.  BASE METAL+ PLASTICS ST.STEEL BACK
FRP Fibre Reinforced Plastic PLASTIC
GC Gold Cap GC
GF Case affixed with gold.  GOLD FILLED ST.STEEL BACK
GHA Case coated with hard titanium nitride. (Surface hardness is high resists against small scratches. Hv = 1200).  GHA ST.STEEL BACK
GPBCR Gold plated and black chrome plated case.  BASE METAL ST.STEEL BACK
GPCRP Gold plated and chrome plated case.  BASE METAL ST.STEEL BACK
GPCRP.GP Gold plated and chrome plated case. Back side GP BASE METAL
GPDP Case combining gold and palladium plating.  SGP + PDP ST.STEEL BACK
GPDP.GP Case combining gold and palladium plating. Back cover GP SGP + PDP SGP BACK
GPHC Case combining hard coating of titanium nitride.  BASE METAL ST.STEEL BACK
GPHGC Case combining hard coating of titanium nitride and gold plating.  BASE METAL ST.STEEL BACK
GPRUP Case on which the ruthenium plating was applied on the gold plating.  BASE METAL ST.STEEL BACK
GPWD Gold-plated case, combined with reinforced wood.  BASE METAL + WOOD ST.STEEL BACK
HC Case coated with hard titanium nitride. (Surface hardness or resistance to small scratches, Hv = approximately 1200)  BASE HC ST.STEEL BACK
HC.SSHC HC bezel and middle with combined SS and HC back BASE HC ST.STEEL BACK HC
HCBCRP Coating of hard titanium nitride and the side subjected to black chrome plating.  BASE METAL ST.STEEL BACK
HGC Case coated with hard titanium nitride.  HGC ST.STEEL BACK
HGCPC Case combined with plastics by applying a coating of hard titanium nitride.  HGC + PLASTICS ST.STEEL BACK
HGP Hard gold plated case. (Surface hardness is high and resistant to small scratches. Hv = about 500) HGP ST.STEEL BACK
HSS Case made of hard stainless steel. (Hv = about 450) STAINLESS STEEL
HTIAGP.HTIA Part of the hard titanium alloy on the case plated with gold TITANIUM ALLOY
LSGP Light colour SGP SGP
MCOA Cobalt hard alloy case. (Excellent in corrosion resistance and strong against small scratches. Hv = 500) Edge / Back SS COBALT ALLOY ST.STEEL BEZEL.BACK
MHC SS case coated with hard titanium nitride.  BASE METAL ST.STEEL BEZEL, BACK
MSS.HC SS middle with hard titanium nitride bezel and back ST.STEEL + BASE METAL ST.STEEL BEZEL
MSSGP Case of SS plated with gold ST.STEEL + BASE METAL ST.STEEL BEZEL,BACK
MSSPCD SS bezel combined SS and plastic middle with SS back PLASTICS ST.STEEL BEZEL
MTIGLC Titanium coated with glass (surface hardness is higher than ordinary titanium, Hv = about 350-400) and SS.  TITANIUM ST.STEEL BEZEL,BACK
NSA Super hard alloy side. (Surface hardness is high and resistant to small scratches, Hv = about 1200). ** NSA STEEL BACK
NSACG A part of the superhard alloy was coated with hard titanium nitride. ** NSA+NSCG ST.STEEL BACK
NSAG Super hard alloy case. (Surface hardness is high and resistant to small scratches, Hv = about 1200). ** NSAG ST.STEEL BACK
NSAGCE On the part of the case where the super hard alloy and ceramic are combined the coating of hard titanium nitride was applied. ** TUNGSTEN CARBIDE + CERAMICS ST.STEEL BACK
NSB The case sprayed with hard material such as ceramic. (Surface hardness is high and resistant to small scratches, Hv = about 700-1000).  NSB ST.STEEL BACK
NSCG Case of super hard alloy coated with hard titanium nitride. (Surface hardness is high and resistant to small scratches, Hv = about 1200). ** NSCG ST.STEEL BACK
NSCGCE The case combining hard carbide and hard ceramic with hard titanium nitride. (Surface hardness is high and resistant to small scratches. Hv = about 1200) TUNGSTEN CARBIDE + CERAMICS ST.STEEL BACK
NSP Hard Alloy Processing NSP
PC Case made of plastic. PLASTICS
PC.SS Case made of plastic. Case back SS PLASTICS ST.STEEL BACK
PDP Case subjected to bare Palladium plating.  PDP ST.STEEL BACK
PDPRUP Ruthenium plated case on palladium plating.  BASE METAL ST.STEEL BACK
PM Platinum PM
PMP Platinum Plating PMP
SGP Seiko Gold Colour Plate.  BASE METAL ST.STEEL BACK
SGP30 Case with 30 micron gold plating.  SGP30 ST.STEEL BACK
SHA Hard alloy case. (Hv = about 700).  SHA ST.STEEL BACK NICKEL ALLOY ST.STEEL BACK
SHAGHA A part of the hard alloy case is coated with hard titanium nitride.  NICKEL ALLOY ST.STEEL BACK
SHAHC A part of the hard alloy case is coated with hard titanium nitride.  NICKEL ALLOY ST.STEEL BACK
SILP Silver Plating SILP
SILVER Case made of silver. xxx represents value of silver / 1000 xxx SILVER ST.STEEL BACK or SILVER xxx ST.STEEL BACK
SS Case made of stainless steel. It is harder to rust than regular steel STAINLEES STEEL
SS.PCD Part of SS with plastic decorations.  ST.STEEL+ PLASTICS ST.STEEL BACK
SS18K Case of 18K yellow gold and stainless steel combined.  ST.STEEL + 18KT ST.STEEL BACK
SSBCR.BCRP Case of the ss plus black chrome plating. Back cover black chrome plating. ST.STEEL+ BASE METAL BASE METAL BACK
SSGP Case of SS with gold plate ST.STEEL+ SGP ST.STEEL BACK
SSGP.G Case plated gold on part of SS. Ruptured Gold Plating. ST.STEEL+ BASE METAL BASE METAL BACK
SSHC Part of ss coated with hard titanium nitride.  ST.STEEL+ BASE METAL ST.STEEL BACK
SSPCD.BCRP Apply black chrome plating to part of SS, case plated with plastic decoration.  ST.STEEL+ PLASTICS+ BASE METAL ST.STEEL BACK
SSPCD.FRC Fluorocarbon resin was sprayed on a part of SS and the case on which plastic decoration was attached.  ST. STEEL + BASE METAL MIDDLE BASE METAL BEZEL ST.STEEL BACK
SSWD SS case combined with reinforced wood.  ST.STEEL WOOD ST.STEEL BACK
STP Stainless Steel Plating STP
T14K.M14KWG Case combining 14K yellow gold and white gold 14KT ST.STEEL BACK
T14KHC.M14K Case of 14K gold yellow gold coated with hard titanium nitride 14KT ST.STEEL BACK
T18K Case which combines 18K yellow gold and SS ST.STEEL 18KT BEZEL
T18K.MSS18K Case with 18K yeloow gold and SS ST.STEEL+ 18KT MIDDLE 18KT BEZEL ST.STEEL BACK
T18K.MSSGP Combined 18K yellow gold and SS with some gold plating ST.STEEL + BASE METAL MIDDLE 18KT BEZEL ST.STEEL BACK
TALH.MBCRP Hard aluminum case combined with black chrome plating.  BASE METAL MIDDLE ALUMINIUM BEZEL ST.STEEL BACK
TALH.MFRC A coating of fluororesin was applied to the case combined with hard aluminum.  BASE METAL MIDDLE ALUMINIUM BEZEL ST.STEEL BACK
TALH.NSB Case where the hard material was sprayed and hard aluminum was combined.  NSB MIDDLE ALH BEZEL ST.STEEL BACK
TALM.MPC Case on which aluminum and plastic are combined.  PLASTICS MIDDLE ALUMINIUM BEZEL ST.STEEL BACK
TALM.MPCPDP Palladium plating on case combined with aluminum.  PLASTICS MIDDLE ALUMINIUM BEZEL ST.STEEL BACK
TBCRP Part of SS was subjected to black chrome plating.  ST.STEEL BASE METAL BEZEL
TBCRP.FRC.MBCRP Black chrome plating and case with fluorinated resin coating.  BASE METAL ST.STEEL BACK
TBCRP.MFRC Black chrome plating and case with fluorinated resin coating.  BASE METAL ST.STEEL BACK
TBCRP.MHC The coating of hard titanium nitride and the case subjected to black chrome plating. BASE METAL ST.STEEL BACK
TCE Ceramic and SS combined case ST.STEEL CERAMICS BEZEL
TCE.GP Ceramic bezel, GP case BASE METAL CERAMICS BEZEL
TCE.MTIHICDC Ceramic bezel, TI with super hard coating case and back TITANIUM + CERAMIC BEZEL
TCE.TIHC Ceramic bezel, TI with super hard coating case and back TITANIUM + CERAMIC BEZEL
TFRC Part of SS was sprayed with fluorocarbon resin ST.STEEL BASE METAL BEZEL
TFRC.MHC Case coated with fluororesin and hard nitride nitride BASE METAL ST.STEEL BACK
TGP.MCOA Case with gold plated bezel and cobalt hard alloy are combined COBALT ALLOY MIDDLE BASE METAL BEZEL ST.STEEL BACK
TGP.MGPBCRP Black chrome plated and gold plated case BASE METAL ST.STEEL BACK
TGP.MGPDP Case with gold plated bezel and palladium plating BASE METAL ST.STEEL BACK
TGP.MGPHC SGP bezel, SGP and HC case BASE METAL ST.STEEL BACK
TGP.MGPWD Case combined with reinforced wood with gold plating BASE METAL WOOD MIDDLE BASE METAL BEZEL ST.STEEL BACK
TGP.MHC Case gold plated bezel and hard titanium nitride case BASE METAL ST.STEEL BACK
TGP.MHSS Hard stainless steel with gold plated bezel ST.STEEL BASE METAL BEZEL
TGP.MSSGP SGP bezel, combined SS and SGP middle ST.STEEL BASE METAL BEZEL
TGP.TIHCCE SGP bezel, combined TI, HC, and Ceramic one piece case ST.STEEL SGP + SGP BEZEL
TGPCE.MGP Combined SGP and Ceramic bezel, SGP case BASE METAL CERAMICS BEZEL
TGPDP Parts of SS plated with gold and palladium plating ST.STEEL SGP + PDP BEZEL
TGPDP.G Gold plated and palladium plated case SGP MIDDLE SGP + PDP BEZEL ST.STEEL BACK
TGPDP.PD Gold plated and palladium plated case PDP MIDDLE SGP + PDP BEZEL ST.STEEL BACK
TGPGHA.MGHA Gold plated case combined with hard material NICKEL ALLOY MIDDLE BASE METAL + NICKEL ALLOY BEZEL ST.STEEL BACK
TGPHSS.MHSS Case of hard SS with gold plating ST.STEEL + BASE METAL BEZEL
TGPHTI.HTI Rigid titanium case. (Ti alloy hardness was improved in addition to the characteristics of titanium having excellent lightness, ru corrosion resistance, Hv = 300) case with gold plating TITANIUM ALLOY BASE METAL + TITANIUM ALLOY BEZEL
TGP-MTI Case combining titanium and gold plated bezel TITANIUM MIDDLE BASE METAL ST.STEEL BACK
TGPSHA.MSHA Gold plated hard nickel alloy NICKEL ALLOY MIDDLE BASE METAL + NICKEL ALLOY BEZEL ST.STEEL BACK
TGPTI.TI Combined TI and SGP bezel, TI middle and TI back TITANIUM + SGP BEZEL
THC Case of SS coated with hard titanium nitride film ST.STEEL BASE METAL BACK
THC.BTI HC bezel, BTI (Bright Titanium) middle and BTI back TITANIUM
THC.MBCRP Coating of hard titanium nitride and case subjected to black chrome plating BASE METAL ST.STEEL BACK
THC.MHCPCDP HC bezel, combined HC and plastic middle with SS back ST.STEEL + PLASTICS
THC.MSHAC Hard cobalt alloy case subjected to coating of hard titanium nitride, case parts with hard titanium nitride coating COBALT ALLOY MIDDLE BASE METAL BEZEL ST.STEEL BACK
THC.MSSCE HC bezel, combined SS and Ceramic middle, and SS back CERAMICS + TITANIUM
THC.MTIGLC Titanium coated with glass (surface hardness is higher than ordinary titanium, Hv = about 350-400) and SS with nitride coating.  TITANIUM MIDDLE BASE METAL BEZEL ST.STEEL BACK
THC.TIHCCE Ceramic Outer Case, TI HC Inner Case CERAMICS + TITANIUM
THCHSS.MHSS Ferrite hard stainless steel coated with rigid titanium nitride ST.STEEL ST.STEEL + BASE METAL BEZEL
THGC SS case coated with hard titanium nitride ST.STEEL BASE METAL BEZEL
THGC.MCOAHGC Cobalt hard alloy case coated with hard nitride COBALT ALLOY MIDDLE BASE METAL BEZEL ST.STEEL BACK
THGC.MHTI Case combining SS with hard titanium nitride coating on rigid titanium (Rigid Ti = hardness more than ordinary Ti, Hv = about 300) ST.STEEL + TITAN
THGMCETIHG Combination of titanium and ceramics which was coated with hard titanium nitride CERAMICS MIDDLE BASE METAL BEZEL TITANIUM BACK
THGMCETIHG HGC bezel, combined Ceramics, TI and HGC middle and combined Ceramics, TI and HGC back CERAMICS + TITANIUM
THGP Case of SS on which hard gold plating was applied ST.STEEL HGP BEZEL
THTIGP.HTI Case of hard titanium coated with hard titanium nitride TITANIUM ALLOY
TI Titanium TITANIUM
TIHC.TI Case of titanium coated with hard titanium nitride TITANIUM
TIHNT.TI Titanium case which has been hardened by nitriding treatment. (Hv = about 600, Matte finish) TITANIUM
TPCBCRP.MBCRP Black chrome plated case combined with plastic. BASE METAL MIDDLE PLASTICS + BASE METAL BEZEL ST.STEEL BACK
TPCFRC.MFRC Fluorocarbon resin coating was applied and the case combined with plastic BASE METAL MIDDLE PLASTICS + BASE METAL BEZEL ST.STEEL BACK
TPCS Plastic and SS combined case ST.STEEL PLASTIC BEZEL
TPDP PDP bezel, SS case PDP BEZEL + ST.STEEL
TPDP.G Gold plated and palladium plated case BASE METAL ST.STEEL BACK
TPDP.GPD Gold plated and palladium plated case BASE METAL ST.STEEL BACK
TPDP.MPDPHC Palladium plating and case coated with rigid titanium BASE METAL ST.STEEL BACK
TSGP Case of SS plated with gold ST.STEEL SGP BEZEL
TSGP.GPD Palladium plating and gold plated case BASE METAL MIDDLE SGP30 BEZEL ST.STEEL BACK
TSGP.PD Gold plated and palladium plated case PDP MIDDLE SGP BEZEL ST.STEEL BACK
TSGP.SSG Case of SS with gold plating ST.STEEL+ SGP MIDDLE SGP BEZEL ST.STEEL BACK
TSHA Case combining hard alloy and SS ST.STEEL NICKEL ALLOY BEZEL
TSS.PCA Case combining SS and plastic PLASTICS ST.STEEL BACK
TSSCE Combined SS and Ceramic bezel , SS middle and SS back ST.STEEL ST.STEEL + CERAMIC BEZEL
TSSGP Case of SS with gold plated bezel ST.STEEL ST.STEEL + SGP BEZEL
TSSGP.MGP Case of SS with gold plated bezel BASE METAL MIDDLE ST.STEEL + BASE METAL BEZEL ST.STEEL BACK
TSSGP.MPDP Combination of gold plated bezel and palladium plated case BASE METAL MIDDLE ST.STEEL + BASE METAL BEZEL ST.STEEL BACK
TSSHC SS bezel coated with hard titanium nitride, SS case ST.STEEL ST.STEEL + BASE METAL BEZEL
TSSHC.HICDC SSHC bezel, SS with super hard coating, and SS with super hard coating back ST.STEEL ST.STEEL + ST.STEEL BEZEL
TTIGLCGP.MTIGLC Titanium coated with glass (It has a higher surface hardness than ordinary titanium Hv = about 350-400) gold plate applied TITANIUM MIDDLE TITANIUM + BASE METAL BEZEL ST.STEEL BACK
TTIHC.MTIHICDC.TI Ti & HC bezel, Ti & HC middle, Ti Back TITANIUM
TTIHC.TI Combined TI and HC bezel, TI middle and TI back TITANIUM
TTUCAC Hard alloy coated with hard titanium nitride combined with SS case ST.STEEL TUNGSTEN CARBIDE BEZEL
TTUCAC.MGP Case combining a super hard alloy plated with hard titanium nitride and gold plating BASE METAL MIDDLE TUNGSTEN CARBIDE BEZEL ST.STEEL BACK
TUCAC Case of the super hard alloy coated with hard titanium nitride (High surface hardness and resistant to small scratches, Hv = about 1200) ** TUNGSTEN CARBIDE ST.STEEL BACK
TUCAC.SSGP Case combining SS with a gold plate and a hard tungsten alloy coated with a hard titanium nitride TUNGSTEN CARBIDE + ST.STEEL + BASE METAL ST.STEEL BACK
TUCSS Case combining SS with super hard alloy coated with hard titanium nitride TUNGSTEN CARBIDE + ST.STEEL ST.STEEL BACK
TWGP White gold plated bezel with stainless steel case TWGP
WGF White Gold Filled WGF
WGP White Gold Plating WGP
WGPG Gold plated case with gold-plated bezel WGPG

Note **: Although it is hard to scratch it is slightly brittle so care should be taken to avoid shocks such as a drop.