Conn 16B Rosebrook Trumpet
Date: 1923. Instrument owned by Paul Ayick.
This instrument is what I had previously classified as "unknown model French style". A discussion on the Trumpet Master forum has led to the tentative conclusion that this is the 16B Rosebrook Trumpet. The period is correct. The bore size is correct. And circumstantially, all three instruments of this model were found in the San Francisco area. That is relevant, because David Rosebrook , after whom the model was presumably named, was from the San Francisco area.
What is odd about this instrument is the second valve slide. It is pointing towards the bell of the instrument. At the time second valve slides were perpendicular to the second valve and later on pointed towards the player. The "upside-down" third slide is slightly unusual but not unprecedented; several Conn models were set up that way. Although none that I know of in 1923. Paul tells me it is a #1½ (0.458") Bore.