Window channel balance

A quick learner from Crystal Lake, IL says:
Hello, my window has these markings on it. (WSIGCC CBA03 IGMAC WSMED 5-22-95 337E4) The channel balance says (30TG) on it. I'm thinking your product # S751-30 will work, but you don't have option 30TG. The end of the springs break. PN 15-014 (Balanced knife lock shoe) looks like the one I have. Can you help me out?

Thank you,
User submitted photos of a window balance.
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Tom from SWISCO responded:
Thanks for posting. Can you confirm the length of the metal channel? With your stamp, it might be 31" instead, not 30".
A quick learner says:
Length of metal channel is 31". Back of channel is flat, not ribbed.
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Tom from SWISCO responded:
Ah, if it has a plain channel then that changes things. It will have to be custom made. That said, that shouldn't be too much of an issue. Can you tell me how many you need? Can you also confirm how it attaches at the top? Does it screw into the jamb track directly, or is there a hook of some kind?
A home owner says:
6 are needed. It screws into the jamb track, no hook. See first picture. Spring attaches to bar then screw above that screws into jamb track.
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Tom from SWISCO responded:
Great, thanks. I'll send you a custom order form for this balance shortly. Keep in mind there are two choices, depending on the weight of your sash: a 31E for a sash weighing 29 through 33 pounds, or a 31F for a sash weighing 33 through 37 pounds. I will be sending you an order form for each, so just choose whichever best matches your sash weight.
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