Just to update, picked up the tank and confirmed it's an aquarium from glass width, dimensions, and talking to someone at the lfs. Unfortunately the seal around one of the bottom corners is cracked, so I picked up some acrylic aquarium sealant and went to work on resealing the whole bottom of the tank. (ick those fumes are strong though)
Hopefully will see in a few days if my repair job worked and the thing can hold water once more.