window spring balancer

A home owner from sonoma ca says:
Hi there,

I just bought a home build in 1981. It has two broken windows, pretty sure it one of the spring balancers on each one. I have removed the window and I cannot locate any identification of the manufacturer. The casing on the balancer says only "20S27." can you help me. with the dimensions, could I order a new set of spring balancers from you guys? would a picture help?

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Paul from SWISCO responded:
I'm not sure exactly what you have based on just the stamp. I would like to see some pictures of the hardware itself. You can upload your pictures right here for us to see. Make sure to take pictures of the top and bottom of the balance while it is fully removed from the window. Thanks!
A home owner from sonoma ca says:
Here are the images. I was told these were "2020"s. I can't tell from your website which one I would order.

Thanks for your response.
User submitted photos of a window balance.
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Tom from SWISCO responded:
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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