The stock was likely a M91 Infantry rifle stock, but also likely Finnishicon made. Could have even been a M27, M28, or M28/30 stock as well due to the sling escutcheon. Unless there is any specific markings on the stock to date it, it could be any of those variants made which would place the stock somewhere 1908 or later as that was when the sling slots were first cut into the stock for the infantry rifles. If I had to guess this rifle was likely a battlefield pick up by a Finnish soldier with damaged wood. The soldier likely then changed out the wood himself as carbines would have been fairly desired (the M38 is a awesome size for a rifle) and bringing it forward might have resulted in it being sent elsewhere.