It's one of 2 built [identical] by my brother. He started building them in the 70's. They have been built to shoot-slugs and/or flashlight batteries,golf balls,beer cans[full flys better]. Up to a 2 pounder. This one is #28 the last one built. No more to be built.
I paid $10 for this one at a yard sale. It was in a basket. I took it to work, blasted and painted it. 2" bore, and all steel. There's a couple hundred hours of machine work in this thing. I wish the bore was a touch larger. Red Bull cans would fit then. Just think what a plaster filled Red bull can would do to a car door!