I bought one - non-drilled, thus never previously fired, nor proofed - that is how they were sold and how anyone in Canada can actually buy one of their handguns- no vent, not a firearm.
I had to drill the vent hole - fired a few rounds, took it apart to see how well it was made, ie: pulled the breech plug, took a bunch of pictures, took some measurements, then reassembled it and sent it back & got a refund.
The forend swivel screw was an oversized 8x32 in what seemed a 10x32 threaded hole. I was to find the breech plug was of quite similar quality.
From the outside, apart from the reddish non-water proof stain and finish which came off together as one mixture, it indeed looked like a Sea Service Brown Bess.
The breech wall was slightly less than .1"- about .095" thick to the bore at the vent, then tapering down rather quickly towards the muzzle.
Only 3 threads were engaging on the breech plug (oversized 7/8" thread in an oversized threaded hole- ie: not standard and not metric, either - the barrel threads appeared to be very rough, but not hand filed, those 3 bearing threads had varying amounts of engagement, comes to mind - .005", .011" and .022"- just from memory. Those breech plug threads were in barrel threads running some .037" deep.
I assume to prevent a LOT of blow-back/leakage around the threads, they incorporated a flash shield between the tang and barrel, .010" thick. This was part of the breech plug and tang and pressed against the back end of the barrel. This is what stopped the blowback of fouling from erupting from the back end of the barrel around the threads when it was fired. Very clever, but of course, even more scary.
The threads were undercut at this "flashing", like some/most? guns smiths undercut modern rifle threads at the barrel's shoulder. The undercut (radial gouge) was approximately 3 threads in width, but running all the way around the flashing 360 degrees. When I pulled the plug, the barrel threads and this trough around the plug were packed hard with fouling. The flash -plate I will call it was actually a good fit against the rear of the barrel - good thing.
It was scary to behold - even scarier was the thought that I had fired it. It sure was a good sparker - that much was good - that is, after I ground of the 1/16" deep (some almost 1/8" deep) cross grooving they'd cut across the face of the frizzen - I expect to 'catch' the flint? The gun could not be fired without first grinding off the frizzen face's cross grooving as it would have simply disintegrated the flint first attempt to fire. It did have a good strong spring as well. 2 positives?
This lack of attention to detail should have been a warning to simply send it back, unfired, but no, I didn't do that. I still thank my Guardian Angle for sticking with me.