Coil Balance Springs

A quick learner from Allentown, PA says:
May 4, 2020
Springs (both) are broken in my vinyl double hung windows. They are 1/2 inches wide with a short tongue (attached with a screw to the "rider". The only marking near the tongue is a capital letter D. The sash weighs 11.5 pounds. The closest item in your catalog would be the series 152 spring. Am I on the right track? I don't understand why both have broken in the middle - window installation in 2001. It is the bottom sash with problems, though.

Thanks, be safe,
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Bob from SWISCO responded:
May 6, 2020

Thanks for posting. The coil balances used depends on the identity of the pivot shoe they connect to. Can you remove the balance system from the window and show us this pivot shoe? From there, we'll be able to confirm what you need. Thanks.
A quick learner from Allentown, PA says:
May 18, 2020
With regard to my post of May 4 and your reply of May 6. Attached are photos of the pivot shoe and associated parts with measurements.
Thumbnail of the uploaded file named IMG-1770.JPG
Thumbnail of the uploaded file named IMG-1769.JPG
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Bob from SWISCO responded:
May 18, 2020

Thanks for getting back to me. This looks like a 15-175 Pivot Shoe. This shoe uses our Series 152 Coil Springs. To know what spring weight to select, look for a stamp code on the coil tape. If there is none, or you are uncertain, obtain the exact weight of your window sash. Give us that exact weight and we'll work out what you need. 
A quick learner from Allentown, PA says:
May 19, 2020
Upon reweighing the sash I find it weighs 12.5 pounds and we saw the capital letter "D" stamped on the spring. As both springs are broken, we need two springs. I thought the #152 spring was what we needed. It appears that there is no spring that handles the half pound so do you go up to 7 lbs per spring or go with 6 pounds?
We will also need a Tilt window latch, Left hand (26-243). We have measured the size and the 11/16" width matches what we have.
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Bob from SWISCO responded:
May 19, 2020

If the window weighs exactly 12.5 lbs, you'd be fine with using just one S152-6 6 lb Coil Spring on each side of the sash, for a total of 12 lbs of support. You are fine with coil balances if you are within 1 lb of the actual weight. All parts can be ordered directly through the online store. When you find a part you want, simply click "Add to Cart," and then click "Checkout" at the top right hand corner of the screen. Don't forget to set the quantity you desire.
6 lb Series 152 Coil Balance
6 lb Series 152 Coil Balance
S152-6
$4.80
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