Miller,
In my unlearned opinion your drilling was proofed in Zella-Mehlis, consequently was likely made in or near there. Zella-Mehlis started dating the proofs and showing ledger numbers before 1911. Suhl started dating them after 1923. I believe your reading of the date is correct. It is possible to have one barrel replaced, by German workmen, but it won't be cheap.
Mike