Argentine carbine

Finally got around to working on my Argentine carbine stock. The finish was black and smooth, and looked like a bowling ball. The finish must have been shellac as the only thing I found to attack it was alcohol. After hours of work, I find this stock has no cartouches, and the serial # on the forearm is over stamped. The numbers appear to be made by the same stamp and look original. All the metal sits flush and I can see no evidence of sanding. Don't know if this is a mountain carbine or an engineers carbine. Also, there's a tiny, maybe 1/8" star on the bottom side of the grip. What have I got here? By the way, how is the butt plate finished? Best, Dan