I think this may be an altar box, perhaps designed to hold long sticks of incense. From the photos, the box appears to be complete and made without a lid. A lid would have been unnecessary on an incense box, as sticks would have been frequently taken out and burned as offerings to ancestors or deities.
Dragons are a common motif on Chinese altar boxes and reliquaries as early as the Song Dynasty, though this observation is not conclusive regarding the origin or function of this box.
The hallmarks do not look Japanese to me, especially the lack of a jungin mark on a piece with some age. If it is not Chinese (as Rauls says), could it be Straits silver or perhaps made by for export to Tibet or a SE Asian Chinese Buddhist community?