And for really tough ones there's these.
I traded for a small batch of them back around 1981. 74 McCovey Washinton And maybe a couple other cards for the whole bunch.
The stupidly traded half of them for another McCovey Washington.
So there's around 10 of them out there plus my 10. I've never seen any others and haven't seen them listed anywhere.
Pretty interesting, along with the different colors most are screened more coarsely, and there are a few reversed negatives. And numbers over 150 - which seem to match the list for proofs in the Standard catalog.
Steve B