Thanks for the pix Monty. Forgive my dullness, but I still don't get it. How does the screw go from the inside out? Through the tumbler shaft itself? Maybe I'm missing something?
Some Euro work - you can find it in most countries, it's not distinctly German, although there are varies approaches - will utilize a tumbler that instead of the square key portion (protruding through the lockplate) being threaded with female threads, will carry a shaft with male threads and a "nut" so to speak is then threaded on to it from the outside. Brits used it on a number of locks, particularly 19th century, and the nut was slotted and tightened with a special driver that was basically a standard screwdriver with a hollow or relief in the center of the blade to allow clearance for the male threaded shaft.
The rifle illustrated here by Monty looks as though it *might* use the typical male threaded shaft with the portion in the center of the decorative nut (just going by the photo) being the exposed end of the shaft, which may be also threaded and then deocratively filed to blend in with the nut. I say might - Monty obviously would be better suited to explain his own rifle. The rifle illustrated here as the brass barrel piece does not seem to use a through-shaft, so the outer decorative 'nut' conceals the whole thing. I'm not sure how they were tightened; I'd guess careful tapping with hardwood or soft (brass or copper) punches/chisels to tighten.
I've not personally seen one with a true separate screw from the inside, i.e the tumbler drilled through and a screw going completely through the tumbler to thread into the nut. Not sure how that could be done if still retaining an internal tumbler shaft/axis to work with a bridle.
