Lol I posted the link in prior comments too "Black Beauty Coin", didn't find the thread until after. OP says it should be proof and aside from these I've found six proof coins this week alone all circulated; Always better to ask
Would you be able to tell me if there were by cupronickel planchet errors for Kennedy prior to the transition. I have a 1966 weighing 11.34 but the rim is dark colored like my other 40 % coins
There isn't much difference between 11.50 grams and 11.34 grams; that may be within Mint tolerances, I don't know. How accurate is your scale? Chris
'64: 12.50 grams '65-'70: 11.50 grams '71 to date: 11.34 grams But .16 grams could just be mint tolerance variation as Chris said, or that much could wear off in circulation.
I calibrated before I started weighing and the other coins came up correctly, so that one seemed off.