Conn 86I New Wonder Euphonium
Date: 1927. Owner unknown. Previously owned by University of California San Diego
From the combination of the serial number/date of manufacture, the fact that it is bell up and has four front action valves I deduce that this instrument is almost certainly an 86I. The 86I was produced between at least 1924 and 1927. I suspect production ended in 1929 but I am not entirely sure about that.