I have a set of those from WWII that were made for the military. They show different enemy airplanes at different angles and different ranges. I spent many hours looking at that and can still name WWII aircraft from just a glance.
There was a collectible website that had one for sale for several thousand dollars. I contacted them and asked if they wanted to buy another one. They offered a couple of hundred bucks. I asked why the difference. They didn’t answer. Anyway, I still have it.
any way to get pics?
Have you considered selling the set online?