I would bet that this was a double rifle in a previous life.
probably .450 or .500BPE.
The serial number should not be on the action flat, but on the grip tang.
The tang was probably changed from pistol grip to straight when the gun was rebarelled and restocked.
I need to look at my guns patent numbers, but I would venture to believe an early 1890s gun, maybe SN 13477 instead of 16477.
More to come.
WC-