This guy is a 1987 sculpt by Michael or Alan Perry for the Rogue Trader era of Warhammer 40K. He’s one of the Space Dwarfs / Squats.
Like the rest of the RT301 Space Dwarf range, he has a gun related name – Mauser was/is a German arms manufacturer.
Metal Rogue Trader Squat or Space Dwarf Mauser Von Dreyse