I did some research on the KIM-1 versions.

What I found is:

1976 seems to be the first year a KIM-1 was sold, no version information. Must have had the 6502 with the ROR bug!
Quickly a Rev A and B appeared. All with the MOS label in the right upper corner. Some had serila numbers starting wit a prefix M.

When Commodore took over MOS Rev D to G appeared, with a different keyboard, the SST switch moved to the other site, the keys are more rounded.
According to the handwritten serial numbers production was done at Santa Clara (SCxxxx) or Pennsylvania (PAxxxx) .

I have a page with images of KIM-1 revisions at http://retro.hansotten.nl/6502-sbc/kim- ... revisions/ with front and (if available) backside of the SBC.

Interesting to see the KIM-1 kept the original specifications, and the same color axial capacitors (the yellow ones)!

How many KIM-1s were sold? If I look at serial numbers and interpret as sequence numbers over 50k?

Was there ever a Rev C?

http://retro.hansotten.nl/wp-content/up ... M1PCBA.jpg

Estimating numbers from serial numbers is always a nice idea! You do in general need to try to guess at the scheme used for numbering - fairly likely to be in production blocks.