I think you have a 1948, because it looks like a "JC" to me.
The badge on the front of the machine. Does it have a blue ring with the dates 1851-1951? That would indicate a Centennial machine. If it's a black ring, or just solid brass, it lends to the 1948 date.
Definately not a 1904 machine, they didn't have the 15-91 then.