Version .... Honda Code ................. Frame number ........... Date of manufacture
MK1 ......... CRM250Rk/k2 ................ MD24 10xxxxxx ........... (1989-90)
Mk2 ......... CRM250Rm .................... MD24 12xxxxxx ........... (1991-92)
Mk2.2 ....... CRM250Rp/p2 ............... MD24 13xxxxxx ........... (1992-93)
Mk3 ......... CRM250Rr/r2 ................. MD24 14xxxxxx ........... (1994-96)
AR ........... CRM250ARv/w/w-2 ......... MD32 xxxxxxxx ........... (1996-98)

Engine numbers follow the same system. The engine number can be found at ~10.30 of the clock from the kickstart shaft and is on a tag sticking out from the RHS crankcase.

There are bikes around with frame and engine numbers that don't match Mks that are apparently perfectly legal. Sometime in the past the numbers have been changed or reapplied for whatever reason . More often the engine or crankcases have been changed and this needs to be notified to the DVLA. Sometimes there is no engine number on the V5C.

The one thing you need to be sure of is that the frame number (and engine number if it is on the V5c) matches the number(s) on the V5c certificate for that bike.