I have had several of these. Lg 54MG is a Lg 51 with a detatchable magazine on top of the cylinder.
BlueBook states it has a "rotery"! magazine, but I would describe it as a gravity feed bowl. It is a bayonet fit to the cylinder and you take it off to reload. If you want to shoot pellets directly in the barrel, you have to
exchange the ball-magazine to a blank mag. Warning! if you shoot pellets with
the ball-mag i place, you will pop the glass lid on the magazine and destroy it! Been there... done that....
Sorry no pic`s found in my files!
Regards! Matts