Now that there is a service for researching Finnish military weapons through the national archives, it's made collecting these rifles more interesting. They archived an enormous amount of military documentation from WWII and starting a digital archive about a decade ago. In some cases, it's possible to track provenance to individual units and service members. The research service is available here at www.mosin.fi.
I recently bought this particular m/39 off the EE here because its serial number was listed on an index of rifles available for research on that site. Turns out, it's got a very cool history. It was assigned to a very interesting Estonian volunteer infantry regiment of the Finnish army, which served in combat in the summer of 1944 during the Soviet Karelian Offensive. It was called "Infantry Regiment 200" or Jalkaväkirykmentti 200, JR 200 and consisted of two battalions and supporting companies. This particular rifle was assigned to the 1st Company of the 1st Battalion. We know this, because it was inspected with the rest of the company's rifles at Jalkala village in the municipality of Kivennapa in the Karelian Isthmus on May 8th, 1944. Here is the document from the archive confirming this information:
The unit deployed to the front a few weeks later the first week of June 1944. They served in The Battle of Vyborg Bay, having to retreat due to overwhelming Soviet attacks. They suffered about 50 KIA and 100 wounded in the combat. Here are some photos of the unit from the Finnish national media archive SA-Kuva:
In August of 1944, the Soviet Union began a massive offensive into Estonia and this unit was called home to defend the homeland. This unit was deactivated on 16 August, this rifle was turned in on 17 August, and the men shipped back to Estonia on 19 August. Upon landing in Estonia, the unit stayed together and constituted a new Wehrmacht regiment under the command of
General Wilhelm Hasse. They fought at the Tartu Front and stayed together until the end of the war. Many of them went on to become prominent Estonians. They had the nickname "Finnish Boys" and had a special anthem for their regiment:
Anthem of the Estonian volunteer regiment in the Finnish army 1943 1944
Not often you can find out this kind of history from a surplus military rifle!