balance spring 3540 which is 35 inches long

A home owner from Boonville mo says:
September 12, 2014
I need to order a 3540 balance spring with the ends shown in photos. Please advise on what replacement part number I need.

Thank you.
User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
September 15, 2014
Hey, thanks for posting. I've narrowed this down to two possible channel balance Series: either our Series 351 or our Series 390.

Now, as you can see, the only difference between these two Series is their bottom shoe. The Series 351 uses the 15-002 while the Series 390 uses the 15-001. 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.
Comparison of <a href='Channel-Balance-Shoe/pd/Replacement-Sash-Support-Channel-Balance-Shoes/15-001'>15-001</a> & 15-002
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