Floor vent thing..

I don’t have a photo and so I’ll apologize now but I was inspecting a house yesterday that was built in 1947 and in the basement there was a hole in the tile with a floor grille over it. The actual hole was 8"-10". When I looked in there all I could see was dirt and dust (and worms). It wasn’t a part of the current HVAC system but didn’t look like a floor drain either. Any ideas what it could be?

Edit: I realized I do have a photo!

I would suspect previous hvac not properly removed.

Usually a good idea to check those type for asbestos.