Finland/Russia Stamp

Good Afternoon, I am new to the stamp world and have inherited a Bankers box of Foreign Stamps. my Son and I have really enjoyed digging through the box. Some are identified and others or loose, then there are the ones in envelopes with no identification. we have been able to locate the country of origin for most but I have been have a very tough time on one in particular. I think is an early 1900's but it has an overprint that is really confusing me.

My Son thinks its so rare that it isn't even in the catalog and he has already picked out the new house we will buy when we sell it.

Can anyone point us in the right direction as I can't find it in the Finland or Russia resources I have found.

Thank you

Eric

Civil war era overprint, from 1919. Overprint: Northwest Army (led by general Judenitsch).
In Michel Katalog Ost-Europa nr # 3. Unused value in 2005 is 5 euro. These stamp usually worth much more used and especially on cover.
Sorry.
-edit:
Here's a link to a e-bay listing:
http://www.ebay.com/itm/1919-NORD-W...em5b06c7468a

Thank you. I will have to break the news to him it's not worth millions.