Shot concentrator marked R.G.M

One the top of a shot concentrator is marked R.G.M. I believe the item is French or German. Can someone help with the intials?

rgm or mgm ?
picture please

RGM (or DRGM) = Reichsgebrauchsmuster. It means that the design was registered in the German empire. Sort of a protected design.

Thank you for the information on R.G.M. Here is the item. it has a lead slug base punched crimped to a brass slotted tube. Two strings cross between slots through a cavity filled with sawdust. The blue paper cap is marked as best as I can read R.G.M. yet Boger. It is approximately 16 gauge. I suspect the sawdust filled area is for shot but I am receptive of other suggestions.