The letter “B” below the caliber is believed to be the barrel makers stamp, Bauska Barrels. On this example, the caliber “58” is stamped on the top flat behind the rear sight. The earliest rifles generally had the caliber stamped somewhere on the barrel. On the very earliest rifles, the full name “GREEN RIVER RIFLE WORKS” without the address was stamped on the top flat of the barrel. In the end, converting back and forth didn't offer much so I left it flint and sold the percussion parts.The information that the company stamped on the barrels of factory made rifles varied over the years. My first long rifle had a Siler percussion lock and a drum, but I later converted it to flint by adding a touchhole liner and a Siler flint lock. Another possibility is that whoever built the kit bought a drum with the right threads and a percussion lock.

I've never heard of TC making a convertable, but I guess it's possible. The 'K' serial number of your rifle indicates it was originally a kit (as does the browned barrel). I don't know how many times that steep downhill thing has got me, you'd think I'd remember to aim low! Took it on a cow elk hunt a few years back in Colorado, muffed my shot, almost straight down and shot over her back. Oh, mine has double set triggers and the barrel is brown. It has a beautiful walnut stock and nice brass patch box, but then all TCs I've seen have pretty nice wood. I'd like to know the story behind my gun. Now that I'm all curious I'll contact TC and see if they know anything. I've never seen another TC with a drum&nipple. Maybe I have the only one they made or maybe it was a factory custom/option, I don't know.

But it is a factory barrel, marked 'Thompson/Center Arms, Rochester, New Hampshire, CAL50. Your description is dead on, the drum comes off and a touchhole liner goes in, then just switch the lock to the flintlock.

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