A larger/better scan would help to say for sure, to me the face value (or what is to be seen under postmark) seems like '5' in which case it would be Finnish stamp. I'm sure you know the differences in design (as illustrated below):
Top row Russian, bottom Finnish

The Russian stamps were removed from public sales in Finland May 1911 and replaced with new design that is identical to Russian stamps of the time except face value in Penni(both in Russian and Finnish) as illustrated above. The Russian stamps remained valid domestic postage up to late 1917 (along Finnish stamps), and they were actually required for all overseas mail till early 1918 as the stamps of Finnish Grand duchy and Republic of Finland were not recognized by UPU before.
-k-