Replacement balance(s)

A handy person from Cape Coral. FL says:
This is for a single-hung window.

I could not find any identifying markings, etc. Pictures are attached.

Length 30" and width is 1/2".

User submitted picture of channel balances for NuAir windows.
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Tom from SWISCO responded:
Thank you for submitting your pictures, Tom.

We're going to need a few more pieces of information from you before we continue.

First, since your channel doesn't include any stamps, please give us the weight of the window sash so we can determine what strength you'll need.

Second, please take a look at this attachment guide and see if you can identify your bottom attachment:
Swisco Channel Balance attachment guide.
A handy person from Cape Coral, FL says:
Looks like it's attachment #15-004 (has wings and measures 1 3/32)

Window sash weighs approx. 15 lbs.
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Paul from SWISCO responded:
Thank you for the information. In that case, please take a look at our S385-30 Channel Balance with a 2920 stamp option.
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