"Tags"
One of the charms of collecting K-31's are the possibilities of finding a "tag" under the buttstock of the rifle. It gives the rifle a little more "personality" in my opinion. As you may know military training was (and still is) required for all able bodied males in Switzerland. The part that most find interesting is that in many cases the soldier took his issued weapon and required gear home with him when training was completed. The idea being that if there was a national emergency a large number of soldiers could show up prepared to fight.
So far a little more than half of my K-31's have come with tags. These tags contain information about the soldier who was issued the weapon. Not all tags have a soldiers information on them. Some seem to only have arsenal information written on them. Perhaps these were weapons that were in storage, not having been issued to an individual solder.
Here are some examples of the tags that I have found.

This is my interpretation of this tag:
Rudolph Zust, born 1932
Heavy Infantry Co. 4, 83rd Battalion
Horgen (town?) Zurich (canton?)
3 Obstgartenweg

This is my interpretation of this tag:
Rene Rudolph von Ruhr, born 1930
Infantry Co.2, 99th Battalion
Basel (town)
66 Daumerkirch (sp?) Street
Many K-31 owners have taken the time to try to contact the original owners of their rifles. Quite a few have had success and have recieved letters in return. Most of the original owners speak fondly of their "old rifle" and often include interesting memories or memorabilia with there return correspondence.
With the advent of the Internet it is possible to search the online Swiss phone directories and find out if the original soldier still lives at the address on the tag. I'm told that often in the smaller towns that if the soldier no longer lives at the tags address there is often a friend or relative that will recieve the note and pass it to the original owner.