That "red dot" safety is certainly a post-1952 replacement, as Steyr started marking safeties this way on their model 1952.
Here is (again) my M1900 Mannlicher-Schoenauer. It is marked "MODELL 1900" on the receiver ring and "STEYR 1901" on the left receiver wall. The Steyr serial number is 98, the second lowest recorded so far. Additionally, it is marked with the George Gibbs, Bristol, number B 3452 on receiver and barrel, on the triggerguard with another, Purdey?, one, A808. Remains of origial London proofs, no Austrian ones. Rechambered to 6.5x55 SE and reproofed by the Birmingham proofhouse in 1983. It came to me as a 27" barreled action only, with the original sights, without a stock. A sorry item, but it came for free, as a present. As you see, my restocking job is not yet completed. It still needs some finer shaping, finishing and checkering.