Conn 6H Symphony Small Bore
Date: 1925. Owner unknown
The 6H has #3 bore (0.500"), and was built from 1919 (but possibly earlier) to sometime between 1926 and 1930 and reinstated from 1937 to probably 1979 as the 6H Victor (see separate entry).
What Conn said in 1925:
The Symphony Model is exceedingly popular for orchestras, generally being used for first trombone.