In the SAAC 4th edition registry (that had Kirkhams in it), there are are cars identified with either the KMP or KMPS prefixes. KMPS was initially for small block cars, but they stopped using KMPS after the 40th small block car.
The registry also show longer numbers starting with KMP259, which has the longer number KH3CNLC0259. So it appears that KMP259 is an abbreviated version of the longer serial number.
So I guess the following tag would use the abbreviated number KMP656:
