I had one, briefly - the vent was undrilled, however the breechplug has a big side slanted V in it's face, so if and when a vent was drilled, the vent would lead to the powder charge. It's breech plug had 3 threads of engagement behind this V, with an average purchase of .022"- which was less than 1/2 of the thread depth. The threads were somewhat over 7/8 x14, so a new, proper fitting plug would have to be custom made. It had a washer as part of the tang, which bore against the breech end of the barrel. The tight fit of this 'plate' against the back end of the barrel, is what keeps the pressure inside. The finnish and stain came off on my hands when it got damp in a sprinkle. For it's $750.00 cost, I actually expected more.
(notice I didn't mention the threaded screw holes (sling swivels, etc) were close to 10x24, however the screws were close to size 8 x24 - thread count might have been different - the fit was as noted)