journeymen,
Yes, it could be the 360- 2 1/4", the 9.3x57R is the German designation for the same cartridge. A lot of German cartridges were based on the nominal 360- 2 1/4", some longer, some shorter and some with different diameters of bullets. Brad Dixon has a whole chapter in nis book, dedicated to cartridges based on that case (cases with head diameters from .427 to.434" with a rim are based on the 360).
Mike