Replacement Sash Support Coil Balances

A home owner from illinois says:
February 19, 2020
I have a coil balance that is broken, the only identified marking is a "F" on it. What is the correct coil I need to purchase to replace this and any associated parts? Thank you.
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Tom from SWISCO responded:
February 20, 2020

Thanks for posting! I think I have an idea of what this balance is, but I'm not 100% sure. To confirm, can you show me a picture of the pivot shoe to which it attaches? That acts as a sort of "key" and allows us to figure everything else out.
A home owner from illinois says:
February 20, 2020
Thank you. What the coil fits is this:

Coil Balance Shoe, Slate Blue
Code: 15-177
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Paul from SWISCO responded:
February 21, 2020

If your pivot shoe is our 15-177 you mentioned, then our Series 152 coil spring will work with these. This coil is screwed onto the pivot shoe with the 33-071. With your coil being marked with an "F", it tells us the spring holds a sash weight of 6 pounds. Therefore, our S152-6 should make for a good fit. Have a look and let us know what you think. 
Coil Balance Shoe, Slate Blue
Coil Balance Shoe, Slate Blue
15-177
$3.47
6 lb Series 152 Coil Balance
6 lb Series 152 Coil Balance
S152-6
$4.80
#6 x 3/8 SS Pan Head Screw
#6 x 3/8 SS Pan Head Screw
33-071
$0.21
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