I can't find anything about it either.
Its a pretty bridge wherever it is. The Top of the World site lists the places they were taken but not which is which. If they have listed them in order then it would be Kärnänkoski but if they haven't it won't be.
Stunning stamp, and I love how the 1 has been incorporated.
I believe this is Bridge in Winter from Kärnänkoski voted the 6th most beautiful Finnish stamp of 2014
I'd also vote this stamp among the best of the year!