Check the Switzerland - Milsurp Knowledge Library (click here)
There's an MKLentry for a 1941 Swiss Model 1931 Short Rifle (K31) (click here)
The rifle displayed in the picture virtual tour there has "all matching" serial numbers, including the bayonet, scabbard and frog. Even the sling is manufactured and marked "E. Wirthlin, Mohlin 1941".
Regards,
Badger