What is a Lock number or Serial Number?
PLEASE REFER TO THE ACTUAL KEY LOCK (WHERE THE KEY GOES IN) FOR SMALL SAFES AND CHESTS AND NOT THE SERIAL NUMBER – USE THE SERIAL NUMBER FOR THE LARGER SAFES.
For Small Chests or Files: (Model numbers will begin with 0500, 1100, 1110, 1150, 1160, 1170, 1710, 1900, 1950, 1970, 1200, 1210, 1250, 2100, 2180, 2275, 2460, 6000, 6720, 7150, A3750, A5781, A5865, F2300, F3300, H0100, H1000, H1100, H2100, H2300, H3100, H2300, H3300, H4100, H4300, HD2100, HD4100, KDS-1, KS2100, KS4100, U2101, WD2, WD4, ESB-3, etc… ): A lock reference number is required. It will be a letter, a number, a letter and number, or “blank” (no letter or number), engraved/located on the silver cylinder of the lock (right around the hole where the key goes in at).
For Personal, Home and Home/Office Safes: (Model numbers will begin with: S0 (S0310, S0400, S0407, S0408, S0409, S0410), S3 (S3300, S3310, S3401, S3410, S3417, S3421, S3460, S3467, S3470, S3710, S3807, S3870, S3877, S3910), S4, S5; I0, I3, I4, I5; A3, A4, A5; J3, J4, J5; L0, L3, CS, CSW (CSW3460), DA (DA3831, DA3930), DS (DS3410, DS3431, DSW5781), KSW, MS, MSW, OA (OA3810, OA3821, OA5848), OS (OS0407, OS0410, OS0810, OS3407, OS3421, OS3470), SC, and X (X031, X075, X105, X125)): Indicate your model number and the safe serial number found on the front right-hand side of the door, between the hinges.
http://www.sentrysafeshop.com/Keys-Sentry-Safe-Replacement-Keys-p/keys.htm