Swedish Mauser Micrometer Rear Sight...

[Patrick Chadwick]

The SM backsight types were replacements, and used on civilian target rifles. Military rifles were not supposed to be altered, and thus the only acceptable micrometer backsight was the Västerös micrometer insert, which was a removable add-on for competition purposes, and not a replacement of the backsight leaf, i.e. not an alteration of the original rifle.* See Dana Jones "The Crown Jewels" P. 201-212.

*The BDMP follows this interpretation.