Hi Tom (TH), I'm glad you said with many exceptions!! Mausers are difficult because the on again off again grip numbering system is tough to get a grip on (pun intended). The original K-date grips were numbered, then it appears that sometime in 1935 (G-Date) they stopped numbering grips, starting up again in 1937, then discontinued numbering somewhere in 1939 and starting up again in1940. Numbers continued to the end of production in 1942 (with the exception of the Black Bakelite Grips).
Edit remark: During the periods that the grips weren't numbered, a few were and the periods they were numbered a few weren't!! Don't know why!!!