Circa 1902, American makers of bar steel for tubes used the following marks:

Sanderson Brothers - SB
Midvale - L1
Midvale for military(1899-1900) - H
Carpenter - C
http://www.scripophily.net/castconewje1.html

Winchester purchased their Nickel steel(blanks???) from Bethlehlem Steel.

Kind Regards,

Raimey
rse