what you call a "old mauser" is a gentlemans rifle by the firm "Heinrich Barella Berlin"
Heinrich live from 1819 to 1893 and founded 1844 the "H. Barella Gewehrfabrik" in Magdeburg. think in the 1860s he open a shop in Berlin and with the quality he made became court maker of the kings of prussia. after Heinrich's dead his nephew Max Barella had the shop into to the 1920s, believe up to 1930/31.
like other gunmaker Barella had also a workshop in Suhl for the reputation but practical also for the works to do.

http://forums.nitroexpress.com/showthreaded.php?Number=208106

I would call barella a best gunmaker, there are a lot of interesting big bor rifles with his name and yours is one of this this