I too am a fan of these vintage paperbacks and have quite a large collection myself. Some of the cover artworks are brilliant though, much better than today's books in my opinion.
yes I guess they're a mixed bag, the artwork on mailed fist, the tank crew and gun barrel are taken from the photograph to the left, the tank itself is an amalgam of a Churchill recovery vehicle, Panzer tracks and track guards. Plus the commander has no vision devises and he's standing directly on top of the breech of the 17 pounder. John should have said something, he probably did.