Unknown window balance coil

A quick learner from Chicago says:
June 5, 2022
Hi,
I need to replace a couple of these window balance coils on windows which I am not sure of the original manufacture. Only marking on them has 15 but I don't think the window weights around 30lbs, plus this is a single coil. Also, only the metal shoe is broken at the bottom of these, can only those be replaced?
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Casey from SWISCO responded:
June 8, 2022

Hello,

Unfortunately, the metal cam of the pivot shoe is not available separately but your photo resembles the 15-175 pivot shoe, which is compatible with the Series 152 coil springs. 

If you're not sure which strength option to choose for your coil springs, I would recommend weighing your sash and dividing the weight by two. That will give you the strength option needed to support your sash. Thank you!
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