According to Still, Costanzo, et al Finnish Lugers were supplied by DWM/BKIW between 1923 and 1929; between 1930 and 1933 Lugers were provided by Mauser, some of them have the Banner trademark.
In my experience Finnish Lugers often have mismatched small parts, may be rebarrelled with Tikkakoski barrels manufactured in Finland, have a Parkerized or phosphated finish, and the sights are frequently modified with angular front sights and filed-notch rear.
Original grips are wood, with a circular brass disc inset in the right grip for a property or unit mark. These are usually found with the disc removed. According to Still wood grips were replaced with plastic during rework. I do not know the characteristics of these plastic grips, and don't believe this plastic grip replacement was consistent, as I have seen reworks with wood grips.
--Dwight