Originally Posted by Parabola
Very possibly, but it might also have been chambered for the .577/.450 Martini-Henry cartridge as they too were stamped with a 52 as the nominal bore size.

Certainly.a possibility. Perhaps I'm wrong to think of a dedicated sporting cartridge as more likely than a primarily military one. The action feels a bit "petite" for the larger cartridge, but my ideas of scale are probably conditioned by encounters with military Martinis and not fine double rifles.