Finnish used German M/1909 rifle ammunition pouch.
There were plenty of these pouches in Europe after WW1, and it so happens they fit the Finnish used Mosin Nagant 5 cartridge ammunition clips quite nicely. These pouches became the standard ammunition pouch of the Finnish army and stayed the most prominent one during and well after WW2.
This pouch is in usable condition, although there are many repairs: there are reinforcing rivets on the lid straps and one of the back straps has been replaced. The leather is supple.
There is a manufacturer stamp and 1915 year stamp on the back.
See photos for more details.