These pistols were a topic about the time that I joined these forums. Some people said that there were made in Japan "Tower" pistols that had the breechplugs welded in - not threaded. One fellow posted that he had bought one that had no breechplug at all - just a straight tube!
I bought my first one around 1970, for $17.50 plus $2.00 shipping, from EMF when they were just starting out. Over the years, I've owned several. Always had to harden the frizzens and tweak the locks (internals are soft) to get them to fire with any regularity. And caliber has varied greatly.I always had access through work to welders who would scope (magnaflux?) them after I fired them with an oversized load and cannon fuse for ignition. Never had a problem.
Sold one on a popular on-line auction site about six months ago for $235.00. Granted, it was in nice shape, but there is no way that I would ever pay that much as a buyer. I have no idea why thet sell for the prices that they do; they routinely go for anywhere between $150.00 to $250.00! On that same auction site I sometimes see Thompsen-Center Hawken rifles go for not much more than that. Go figure!
If you haven't already, I'd proof it with a heavy load, fired from a safe distance while around a corner or behind a tree or something. After firing, examine the barrel closely. If you can't get it "scoped" by a welding shop. at least mark some spots on the barrel near the breech, measure (with a good set of calipers) and record barrel diameter at those spots before and after firing the proof load and check for any changes. Changes are bad. This process should be the MINIMUM to check it for safety. If all goes well, use minimum charges in it when you shoot it - no more than 35 grains of powder - and have fun. BE SAFE, but have fun. Good luck.
sneezy