Help ID this rifle

[Chuck White]

I hope it's ok to post this here.
My brother has a rifle described as follows:

23 1/2 - 24 inch  octagon barrel.
It is a trapdoor model.  The trapdoor lifts up and tilts towards the muzzle.  (for loading/unloading)
Chambered for 9mm (don't know what variation) (stamped 9mm on the bottom of the barrel near the receiver).
Stamp on the bottom of the barrel it's stamped "49" real close to the receiver.
Appears to be several proof marks, crown, initials, etc.
The rifle is missing the stock.

Any help ID'ing this rifle will be appreciated.  Web sites etc.

Thanks

[torpedoman]

there is a web site that shows all the proof markings and were they are from and when they were used, the only way to determine caliber is to do a chamber cast using cerrosafe (midway or brownells ) you can melt it in a tuna fish can with a propane torch then measure it and go to cartridges of the world and compare the measurements. Does not sound military it may be a bring back from Europe after WW1 or 2. post a pic it would be a great help someone mat recognize it.

[CannonKrazy]

Post a picture if you can. I would like to see it.

[WILDCATT]

it sound like a european bring back.is it rimfire?they were used for small game.may be belguim/french.