Side load single hung balance spring

A home owner from Jacksonville, FL says:
I have a window that will not stay open. I removed the springs do that I could replace. However, there is no identifying info on the spring itself. I've attached the sticker that was on the inside of window that includes measurements of window. The company that installed the windows is no longer in business. I would appreciate any help you can give!
Thank you
User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
Hey, thanks for posting. I've narrowed this down to two possible channel balance Series: either our Series 380 or our Series 385 balances.

Now, as you can see, there is only one difference between these two Series, and that is their bottom shoe. The Series 380 uses the 15-005 while the Series 385 uses the 15-004. I can't quite tell what you have based on your pictures, though. Please carefully compare their dimensions to your own hardware and see which is a better match.
15-004 and 15-005
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