I think TC is correct. However, there was a water container in a shape like this at "filling stations" to check for an air leak. I don't know the size of the one pictured but I have never seen one made of cast iron. You didn't put tires in it. Back then tires didn't leak, the inner tube did. You take one side of the tire off the rim, pull the de-flated inner tube out, inflate it then submerge it in water to find the leak. Stick a small marker, maybe a match, in the hole, de-flate again, and put a hot patch on, stuff it back in the tire, and you are back in business. I can still remember that smell of a hot patch burning to vulcanize it to the tube. The water pan to check this was quite large because it needed to be big enough to partially submerge the largest tube you might have to fix, truck tubes for sure, and maybe tractor tubes. I think this cast iron "thing" is definately too small for that purpose, and I have seen this shape thing for the purpose T C explained.