MILLER & VAL. GREISS MUNCHEN 10,5x73R what is probably the good old 400 BPE 3" Purdey
https://www.liveauctioneers.com/item/42531374_a-breech-loading-double-barrelled-rifle-by-miller-and
"
Description

dating: last quarter of the 19th Century
provenance: Bavaria
Round, rifled, blued barrels with rib, fore -and rear-sight, decorated with a golden ring at the back, cal. 10.5 x 73; tang finely engraved with floral motifs, with folding peep sight, engraved and blued; backward spring lock signed "MILLER & VOL. GREISS MUNCHEN" around the hammers (restored), featuring fine engravings depicting deers on a side and hounds fighting with a wild boar on the other; receiver with fawns and a deer protecting from a hound; butt and fore-end of fine briarwood, checkered neck and fore-end; horn lever and tail of the trigger guard; trigger guard engraved with the Bavarian crown surmounting the specular monogram of Prince R. Luitpold, engraved iron butt-plate; under the butt a shield with number "2".Luitpold Karl Joseph Wilhelm von Bayern (* 12 March 1821 Würzburg; � 12 December 1912 Munich). This beautiful piece was probably part of a gift received for his accession as monarch of Bavaria in 1886.

dimensions: length 100,5 cm."