Thanks all! I decided to get the Canon. I bought this one:
Looks like a V1, serial# 23922. Seller has 100% feedback and the lens appears to be in great shape. PLus it has the caps, case, and a filter.
While it's for my IIIf, it will find some time on my M4-P
. I know I have an M3 adapter for the 35mm/135mm here somewhere.