Many thanks to Richard Brozenec for sending in this picture of Rosenbach Company motorized tricycle, which he found at the Industriemuseum Brandenburg. We had no idea that it existed!
It was made by the Brennabor company which was based in Brandenburg and was the largest German car producer in the mid 1920s. Apparently the label indicates that the trike was found in Chicago–how it made its way there from Philadelphia is a puzzle we’d love to figure out.
The Rosenbach Company or Rosenbach Galleries was a fine/decorative arts and rare book dealership run by Phillip and A.S.W. Rosenbach from 1903-1953. It was at the Walnut Street address shown on this trike from 1903-1943. This trike must have been used as a delivery vehicle; we know from the company records (which are still housed at the museum) that most customers had their purchases delivered.
Now that we know this exists our next step is to get in touch with the folks in Germany and see what else we can find out about the vehicle. Who knows, maybe there are more lurking out there somewhere.