This is (almost certainly) a Soviet 122 mm howitzer Model 1910-1930,  displayed in Helsinki Military Museum.   The Model 1910 howitzer was based on a French Schneider design. They were produced in Imperial Russia and then in the Soviet Union.  As was typical for most World War I artillery pieces, the gun was modernised from 1930 onwards, the resulting guns called Model 10-30.  One part of the modernization consisted of the addition of a muzzle brake, which is missing on this particular gun.
<a href="//commons.wikimedia.org/wiki/User_talk:Balcer~commonswiki" title="User talk:Balcer~commonswiki">Balcer</a>
CC BY 2.5
This <a href="https://en.wikipedia.org/wiki/photo" class="extiw" title="w:photo">photo</a> was taken with Sony DSC-W50  by <a href="//commons.wikimedia.org/wiki/User_talk:Balcer~commonswiki" title="User talk:Balcer~commonswiki">Balcer</a>