Interesting 1937 Tula 91/30

Acquired this 1937 Tula today...it has some interesting points to it.
It appears completely unrefurbed, but there is a small refurb/rebuild stamp on the receiver.
Total mismatch, you would immediately think SCW at first glance, but it isn't. At first I thought it had the rear sight base pin upgrade, but not so sure about that now..there is a second serial number stamped on the left of the receiver that usually goes along with import marks, but there are no import marks anywhere on it.
Lots of stock repairs.
It is not counterbored.
There is an interesting ink stamp on the underside of the upper hand guard. It is 'DK' or 'OK'. I've never seen this mark.
The only matching part is the buttplate. However the font is different than the receiver, and the buttplate has a slight 'handmade' look to it.
Triggerguard has the older Izhevsk M91 bow and arrow marking.
Finally, the most interesting feature to me are the metal 'shims' inside the stock. Usually one sees work like this on Finnish examples, but this is almost certainly no Finn.
Its an interesting rifle. Enjoy the pics!

Got to looking at this rifle again tonight. Is this a pre war laminated stock? Thought that was a post war thing.

Anzac: I think it's natural wood with unusual grain perhaps. As to the shims I've seen identical examples on Soviet postwar refurbs. The refurb stamp on the barrel is, I believe, one of the known refurb facilities. Neat rifle. My collection is still missing a mid-thirties gun and I'd sure like to find one like this.

Ridolpho

I don't know..that sure looks laminate to me.

Seems to be some writing inside it, but cannot make it out yet.

Anzac: Yes, the grain is unusual but on some of your shots the pattern doesn't appear to have perfectly parallel surfaces as a laminite will. I've seen SCW Mosins with hand-writing in the barrel channel and '37 is within the possible date range, is it not?
Ridolpho

1937 is, but not sure about the serial number. Plus this +one got back to the SU for a refurb, so I doubt this is an SCW example.

However you are probably correct about the wood.