My 4th Edition SCSW has years 1992 and 2000 for the "BKB" prefix:
1992 – BFV, BHP, BHT, BJB, BJC, BJD, BJH, BJJ, BKB, BKZ, BMA, BNA, BNB, BND, BNE, BNN
1993 – BMC, BNW, BNZ, BNW, BPB, BPD, BPE, BPF, BPK, BPL, BPR, BPS, BPY, BRA, BRB, BRC, BRM
1994 – BDY, BRE, BRF, BRK, BRN, BRU, BRW, BSA, BSC
1995 – BSJ, BSM, BSR, BSS, BUB, BUC, BUE, BUH, CAD, CAE, CLS
1996 – CAM, CAN, CAP, CAU, CAZ, CBA, CBB, CBC, CBD, CBP
1997 – CBN, CBP, CBT, CBU, CCD, CCE, CCF, CCH
1998 – CCK, CCM, CCN, CCP, CCR, CCS, CCV, CCW, CCY, CDU, CMH
1999 – BBA, CBD, CBR, CDB, CDD, CDE, CDF, CDH, CDJ, CDK, CDP, CDR, CDS, CDT, CDW
2000 – BAG, BEL, BKB, BKP, BNY, CDJ, CDL, CDN, CDW, CDY, CDZ, CEA, CEB, CEC, CEF, CEJ, CEL, CEM, CEP, CLC
Supica, Jim; Nahas, Richard. Standard Catalog of Smith & Wesson (Standard Catalog of Smith and Wesson) (p. 491). (Function). Kindle Edition.
