M1 Carbine Magazine questions

[ShovelRyder]

I recently aquired some M1 Carbine short mags. They have various stamps. Can anyone tell me which markings are most collectable or rare. I found a website which explains which company made them according to the marks.
They are:

SY-B
R-C
R-O
IU
U (some are parkerized)
UN
SW
UW
K.I.
KSG
U-S:G'
WEP
IW (with circle around both letters)
O.IB
SP (with circle around both letters)
C-Q (the C has an upside down L or T in it...possible JL Clark?)
SL
LI
IS
II
BW
SS
I.A. (letters are underlined)
C-B (the C has an upside down L or T in it...possible JL Clark?)
IA (letters are stamped upside down)
IA
R-C (the C has an upside down L or T in it...possible JL Clark?)
S-O

Thanks

[Scott Wilson]

You should list them if you want help

[ShovelRyder]

done thanks

[JohnMOhio]

SR, maybe this link may help you..

https://www.fulton-armory.com/%5Cfaqs%5CM1C-FAQs%5CCarbinemags.htm

[pickax]

Nice reference, thanks John M !!!

[Tuna]

The US military wanted each carbine to have 100 magazines available. Each maker of carbines had to include magazines with each new carbine. They came in two ways. One marked for the maker of the carbine and then the other being a separate government contract to make general issue magazines. SY-B would be Seymore for IBM but the stand alone U would have been one of the generic made magazines made by Union. Many thought it was for Underwood. Over 600,000,000 magazines were made during WW2 with the majority being the standard 15 round version. All WW2 magazines were blued. Those that are found parkerized were done at Springfield Armory and possibly RIA during the 1950's to help extend the life of magazines.