[Frank]

Jan, I have a K-Date, S/N 3412 that has acceptance stamps of O-37 and S-91, so this must be in the transition range between the O-37 & O-37 and the B-90 & S-91 pistols.

Also I agree that G-Dates were not O-37 marked. I have a very early G-Date and it's stamped just like the late K-Dates with the B-90 & S-91 marks

 

[Frank]

Someone without a lot of K-Date knowledge put this one (S/N 2295) together. There are quite a few errors!!