My theory, please comment:
I believe the shotgun was made pre 1912 and originally blackpowder.
Right barrel flat proof marks: Eagle on top of crowned U on top of 16/1 (meaning Second or final black powder proof, valid such only with a crowned U, Was replaced 1912 by no 17 for Nitro proof, but was still valid until 1939 as final black powder proof. Second set of markings shows crown W over circled 16 (meaning choked barrel, circle used 1891-1945)
Left barrel flat proof marks: exactly as above with the exception of NO crown W.
Higher up on both barrels, identically marked is a chicken looking eagle (similar to the 50's-70s west german markings) with a Faint J underneath (reproof 1951-1971) next to a crowned S (smoothbore 1950-92).
On the watertable are similiar markings but obviously different proofhouses from one verticle set to the other.
No markings on the breechface.
The last set of pictures I posted shows what I believe to be a very tiny either Vienna or Ferlach proofhouse mark, and up by the center lug a Proofhouse mark of later origin.
Of other interest is that the last two digits of the serial number is also stamped on the inside of the trigger gaurd and also on the inside of the forearm release mechanism.
