Another thing about my Luger, the firing pin is grooved, the breech block has a 2 mm diameter hole drilled on the underside and the rear toggle sight blade has been modified to a "u" opening.
check out
http://www.landofborchardt.com/finnishhandbook.html Which is the Finnish soldiers handbook for the M23.
In the book it states they rebarrel with Tikkakoski barrels, groove the firing pin and added a hole to the breech block, They also modified the original rear V notch sight block with a U notch to correspond with the rather wide, untapered barrel front sight blade.
So, with this in mind I am leaning towards my Luger being a Finn without the SA stamp. By the way, the SA stamping started in 1942 according to what I've been told.
However, maybe the 1939 42 Lugers came with the mods to the pin and breech block.
Anybody know?