So the 1870 is estimate, but I read most of the old coins have been cleaned. Done well, you cannot tell Done bad, you may be had Or is it "Done well, you may be had"? I'm getting confused I like old coins but if it's that hard to FIND an uncleaned coin or hard to TELL maybe it's safer to stick to post-1970's error coins. Even I can tell if there is no "s'" on a dime.
I don't know about the date you're using, I sure wouldn't use it. Nor would I limit it to just harsh cleaning. I usually just say that about 80% of all raw, older coins are problem coins of one kind or another. Yeah I know, now somebody wants me to define "older coins". Well that varies with the coins. But a ballpark range - say 1940-1950.
I would agree with Dougs comments - 80% seems to be a fair number that have had something done to them.
Thanks. So what is a "problem coin"? I understand the cleaning thing (if I can even tell) but say I go to a coin show. How would I know a problem coin when I see it?
Honestly, there's a thousand different things you have to learn to recognize. You can have artificial color, and that's not just colorful toning either. You can have altered surfaces - that alone can be many different things ranging from whizzing to a coin being wiped with a cloth. You can have added, removed, or altered mint marks. You can have altered dates. You can have rim dings, gouges, scratches, graffiti. You can have environmental damage like from PVC residue, or any of another thousand substances. You can ground finds, corrosion, pitting. You can have planchet problems, striking problems, toning problems (toning turns into corrosion at a certain point). You have coins that have been over-dipped, and a thousand other forms of harsh cleaning. The list goes on. And to be honest, most collectors can't or won't recognize a lot of it.
