The combination of "S" and "C-S" markings indicate the magazine was manufactured by Scovill Mfg. Co., Waterbury, Conn., and supplied under contract to Colt during WWII. The "S" indicates the Scovill manufacturer and the "C-S" indicates that it was supplied to Colt under a sub-contract. So, originally at least, it would have been found in a Colt-made pistol.
An "L" at the top lip with no other markings would indicate a magazine made (during either World War) by M.S. Little Mfg. Co, Hartford, Conn., as a spare magazine; i.e., not necessarily supplied to a specific pistol manufacturer.
(Info from Clawson's "Colt .45 Service Pistols.")
And, a Merry Christmas to you!
Steve