That will be it then, the base look familiar, possibly from a 70`s Japanese maker set, Nitto ?

I run a number of Facebook hobby groups and many people make up their own playsets, even hire someone to print box art on cardboard boxes for them. Usually they use existing products from various companies. They don't sell them, they just do it as part of their hobby.

1/32nd scale playsets were very common in the 1950s and 1960s, even into the 1970s. And it makes an interesting project to gather existing models and make your own.

Mike Bunkermeister Creek

I've seen "bundles" appear on ebay over the years. By itself, the diorama base may not sell well for the price-point with it's postage cost but throw in an arty set and a nice colour backdrop and it makes it more appealing without increasing the postage cost much (if any). If you paint everything and add basing materials to the diorama you have a nice all-in-one set for a display