Rear sight
Actually this is a rear sight for a m/96 Swedish Mauser, made by Carl Gustafs Gevarsfaktori, designed to give correct elevations with the m/94 round nosed cartridge weighing 156 grains.
The m/38 Rifle is considered by the Swedes to be a Rifle, not a Carbine. The actual Carbines were the m/94 and the m/94-14 with some minor variations such as School Carbines, Fortress Carbines, Engineers Carbines, etc.
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