It's supposed to be "Coppers (that are) heating/selling well on eBay"
The apostrophe is superfluous.
"Copper's (that is, Copper is) heating/selling well on eBay" would just be a declarative statement about the general state of the Copper Age market, without discussing individual books.
Minutiae.
You guys are killing me with this.
Correct use of punctuation can be annoying.
Or is incorrect use of punctuation can be annoying?
My mom was a grammar teacher so I got hammered with proper grammar etiquette growing up. Some of it stuck - one of my pet peeves is the misuse of your and you're; their, there, and they're; to and too; and so on.
Not to say I don't make those mistakes myself and auto-correct nowadays doesn't help but I try to watch it because I think she is still looking over my shoulder
And I never understood why the heck we were taught how to diagram a sentence. Someone's cruel joke who couldn't quite make it as a mathematician and ended up as an English professor, maybe
And to bring the thread back around - I still can't believe how some of these books are fetching such crazy prices. I no longer try to keep up. More power to the sellers and luck to the buyers that some of those comics may actually retain some value.