Assembled by a Czech in the style of a Brno - maybe. You may / may not know but Early commercial
Oberndorfs had no markings except for a serial # behind the recoil lug and on the back of the mag. box.
The ones with DSTs had them installed into the bottom metal v. a separate unit, that's why the underwood ?
As far as a price, strictly ball park $1000.00 +/- 200.00, if however it turns out to be an Oberndorf, it could be quite a bit more. Lets see when more photos arrive. --- John