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Any pics of the back? Doesn't look comp. from the front.

I'd suggest checking with Vince Simonetti and/or Kenton Scott.

FWIW, 3+1 baritone and bass saxhorns were fairly common around the turn of the 20th century, and the in-leadpipe main tuning slide, the length of the bell stack, the compact wrap of the body, the position of the valve cluster, and the "funky" positioning of the valve slides were all characteristic of baritone/bass saxhorns.

Conn had no formal numbering system for the various models until the 20's, and then they started stamping them on the trombones first.

Conn around that time was marketing horns with the tuning before the valves as "baritones",
while horns that tuned after the valves were called "euphoniums".
This particular "wrap" was known as a "short model" baritone.
At the time, horns could be ordered with extra valves, thus the 4th.

Horns were stamped with that 1886 patent (valve port angle reduction) well into the 20th century.
It may have a bore size, usually embossed above the serial number.
My 1908 double-belled baritone has an "S" bore.

The wrap clearly is inspired by the French Saxhorn basse en Si bemol, but the crooks on top of the valve wraps were Conn-only.

Klaus