Possibly. If any coin is Improperly Annealed then they would have the darker color. I think it was a term coined for the late 1950's Nickel probably never used before. The tricky part is determining if it's actually Improperly Annealed or not.
I can now feel like a plastic coating, real smooth, Finally found and looked good at it. I have had it for over 50 years myself. in hand it almost looks like black chrome.Its not paint! I guess its a what the heck did they do to that poor thing coin!
Looks suspiciously like shellac to me. Not that I ever heard of folks coating coins with shellac back in the day..... But then previous generations weren't quite as tuned in to preservation like we are now either. Put a dab of denatured alcohol and see if the plastic feeling finish softens up......... A few years ago my daughter gave me a paper weight that has several beautiful uncirculated pieces encased in a big plastic block. I often wonder what a collector a hundred years from now will conclude when he sees the finish on those coins!
Shellac is great for long term preservation of a coin. It can be removed harmlessly and can prevent almost all damage to the coin from atmosphere or hits/scrapes over the decades..
"Black Beauty" is a misnomer. The coins described as such are ugly. They have thick, black, unappealing, terminal toning. I once saw a dealer with a so-called "black beauty" Morgan in his case. He had a huge markup on it. He was trying like mad to sell the thing - but it was one of the most unappealing Morgan's I've ever seen.
The term is also applied to certain coins which have been improperly annealed. As far as I know, these primarily apply to Jeffersons.