1119954 is the patent number referring to the Haynes Flute Company's patent for the process of creating drawn tone holes. Conn used the process under license and, according to the patent laws of the time, had to list that information on the instrument. The S means soprano. Tenors had a T, C-melody saxes had a C, etc. M153862 is the serial number, a unique number assigned to that instrument that allows one to determine date of manufacture, etc. The L means Low Pitch. At the time your horn was made, the transition from High Pitch (A=453 Hz or thereabouts) to modern concert pitch of A=440 Hz was still going on. All new instruments had to be marked, since the difference was not obvious to the naked eye. High PItch instruments (Conns were marked with an H, naturally) will not play in tune with modern instruments and are therefore undesireable. Most have disappeared over time, but a few crop up on eBay, etc.