I have not been able to find out its age. Any help?
It was sometimes used as a fake name on reconditioned pianos, especially modernised ones. Some Steinmeyers were sold in Leeds by Hopkinson Successors Ltd., but they appear to have been real German makers.
By the 1890s, Steinmeyers were boasting exhibition medals from Vienna, Berlin, Paris and Brussels, but we have no details so far.
1911 Alfred Dolge "Pianos and their makers" includes a huge list of Berlin's piano makers, but there is no sign of Steinmeyer.
1920~ #7,161 Steinmeyer German piano was bought secondhand in 1943, and thought to have been made around 1920, based on Kohler action numbers. This is definitely a German- made instrument, with the typical double touchrail. If your tuner thinks it is safe to remove the action (the working parts of the notes) it may be marked on the back with the action makers' name and number, and I may be able to date this.
1928 My Musique Adresses Universel lists A. Steinmeyer, Berlin.
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If you find old references or links on this site to pianogen.org, they should refer to pianohistory.info