Help With Finnish Overprint

I recently came across this Finnish stamp with a partial cancellation "Ytto". Searching the internet I found reference to "YTTO RAJOITETTU " which in Finland indicates restricted level classified information. Could this stamp have come from the posting of a classified document?

This is most probably a straight line cancel of Ytter, in southern Finland.

Thanks bookbndrbob for that information. Are these type of straight line cancels common? Are they precancels?

Rrogers, I suspect that this is the postmark of a small mail collecting area, or contract p.o. rather than a regular post office. I don't have a reference for these.

In earlier times (than your stamp) a Finnish single line postmark indicated a "bahnpost", or railway postmark.

Not rare in most cases and not precancels.

I believe these were for printed matter (at least). There is no date anywhere with it which jibes with that service.

These are probably best collected on cover since the place names are long enough that you don't get a full name on a single stamp in most cases. These can be found on Christmas cards with no message or a minimal message. Then these were allowed to be sent cheaply as printed matter. Such a card in nice shape today would probably run you about $10-20 or so, so perhaps slightly better than a plain vanilla first-class mail Finnish cover from the same era.