Disclaimer: I'm old and grouchy.
These threads are amusing because of the different perspectives we have on the subject. Here we have what appears to me to be a very modern box of ammo. I'd consider it new, or pretty new anyway. It has no real collector value because its so new. Its value is in shooting it, and maybe obtaining the brass.
I tend to agree the box is probably 1970s production. I recall buying and shooting up a lot of ammo in similar boxes (if not all 32-20). Its good ammo, made since they stopped making the hi-speed stuff that had the ability to disassemble weaker revolvers.
I don't shed any tears for the gun store owner. Yes, he's paid storage on the box for a long time. Or maybe he traded for it from another store that had become tired of paying support on it. Some store owners even buy ammo from estates and bankrupt other stores. I'd guess the original price was in the $5 range. How much did it cost the OP?
A lesson for all here, stop at small and out of the way gun shops. No guarantee of getting an owner who just fell off the turnip truck, but sometimes there are bargains the regulars have no interest in buying themselves. Not just ammo, look for guns an grips and other accessories. I just gave my buddy Joe a box of gun cleaning patches I got with the old house. I'm guessing 25 to 30 years old. Good as new.
On the subject of reloading .32-20s.....good luck. Its not the easiest cartridge to reload. Its probably down on the other end of the chart. Its a tall thin case and easy to crumple. Read about it specifically if you can find anything. Try the internet, its your friend!
The problem is case length. If you trim them all to the same length before you start, you've got a fighting chance. The cases just aren't forgiving of much abuse. Then the next trick is to start very slowly and set your dies for the reloading cycle. Keep remembering the idea you don't want to ruin brass.
If you decide you have a shooter, start looking for components. I scored big time last year. A reloader, or maybe he was a former reloader had a real bargain on lead gas check bullets. He may have cast them himself. They were bulk, like in a coffee can full and two other cans. I bought them all. I'm thinking I paid $10 for maybe 500 or more of them. A steal.
At another gun show A guy had a pile of .32-20 stuff. He had several boxes of loaded ammo (much older than shown above, probably 1930s or 1940s.) He had a couple of partial boxes of loaded and empties. And he had a single box of jacketed bullets, 50 of them. All orphans from some past owner who didn't use them up. It was one of those negotiations that had us both backpedaling. He wouldn't set a price, I knew I was looking at a few hundred bucks worth of stuff. I refused to make him an offer because I dislike overpaying. Finally I was getting ready to move along and he said "How about $85?" Way low, and in my ballpark. I didn't counter offer, I paid up. And he was right, I was going to walk on (never price another man's goods.)
I felt I got a good price. But I don't feel sorry for him. My guess is he doubled the price someone had in the stuff when originally purchased. It seems the caliber is one where components and ammo never gets consumed fully. Gun nuts seem to have the fault of gluttony. We buy and store more than we need at the present time. Our plans are to eventually use our stock piles up, but we die or get even grumpier and the stuff languishes.
The dark corners of our reloading rooms are interesting places. Just like the corner of the gun shop you discovered the box of ammo hiding in. If you take vacations, you might even want to seek out old gun shops. Most of us vacation and do it in a mad rush. We seek to pack every minute into speed limit breaking travel. But if you find a yellow pages, you'll discover many small towns have gun shops. Mostly on back streets and only known to locals. Probably run as a hobby as much as anything else. No employees, only the owner, and sometimes not open on a real regular schedule. Some only on Saturday mornings!
Unusual calibers and even some odd loadings will sit and age like fine wine. Your job is to find them.