I’ve been told they need to be at least 90 degrees to have any real additional value. Having said that, I can’t tell you whether the advice given me is right or not. I’d like to find out myself, John.
Check out the CONECA website. Stands for Combined Organization of Numismatic Error Collectors of America. Great group of folks and quite knowledgeable. https://conecaonline.org/
Well, a quick eBay completed auctions search shows that Morgans sell for a 3x premium or so if they're slabbed. Mine is a G06 raw, so I think someone may bite at $75. We'll see.
Here is my take on the rotation idea...it depends! Basically the thing that affects a rotation premium is whether or not there are dedicated variety collectors seeking out rotated examples. Knowing how popular vamming has become, I would hazard a guess that it will be much easier to get a premium for the morgan versus the buffalo. I can tell you that in my preferred series (seated dimes) there are some dimes that are downright common with rotation (1837, 1839) and others that command a significant premium if found rotated. When looking at coins in general, I believe DEMAND has a much stronger correlation to prices than SUPPLY. This is why something like a 1916d dime in G4 will command more than an 1858o dime in high AU. In all reality, the two coins share very similar mintages and there is likely higher survival rate for the 16d but everyone wants the mercury key date. Did you buy the coins knowing they were rotated, John? Otherwise, it's always a nice surprise when a coin shows up this way. Good luck finding a buyer on each, I think they're cool!
Until a few years ago, the answer was no. Now there are collectors who look for them, so if you can tap into that market, you might get collect a premium. Some early and 19th century coins are almost always rotated. For example I have an 1839-O quarter eagle that was minted with a 180 degree or “medal turn” orientation. That is normal for that issue.
I got a couple that I paid a bit of a premium for both are 180° though. I cracked out this one for an acetone bath to remove the glue.