I've been going through a large batch of 1981 Topps I've had for years. Mostly to find the nicest ones and to be able to get rid of the remainder. Used to be about 15000 cards, down to about 7500-10000. Unfortunately, hardly any over number 528 (Longish story)
Anyway, as I'm going throught them I'm looking for variations, printing errors etc. Most of what didn't get pulled long ago is very minor but I'll be typing up the list eventually. When I'm done I'll post about it.
But I have found one interesting thing.
There are 2 different sorts of backs. There are the normal backs and what I'll call "low contrast backs" sometimes they're a bit hard to pick out, as the pinkish red ink on the back can be light or dark or faded. Here's a scan of an easier example.
The lower one is normal, the upper one low contrast.
At first glance it looks light or maybe faded, but on a second look the screened field behind the stats is actually darker than the normal card while the header panel is lighter. With a high res scan I can see a very slight diffeence in the screen(The dot pattern ) as well.
These seem to be fairly easy to find from the C sheet, a bit less so from the other sheets. Which is strange becasue there should be another sheet they're common on. I'm thinking they're roughly 1 in 20 C sheet cards, maybe the same on the D sheet although those seem more subtle in the difference.
I don't have many at all from the other sheets.
bear in mind that I'm not saying they should be worth anything above a regular 1981 topps, or that any catalog should list them. After all, 1 in 20 1981 topps is still quite common, and even if the other sheets are 1 in 250 that's still common. But they are out there, and would make a nice challenge for a player collector or someone really into 1981 Topps.
The other general varieties are those with yellowish gloss, and a few with a much smoother gloss. There are some cardboard differences too, one I might actually call scarce but I'll do those another time.
Steve B