Find correct balance

A home owner from San Diego, California says:
October 22, 2023
I want to find the correct balance for Milgard Aluminum windows from the early 90's. This is a block and tackle style balance. The metal portion of the original balance is 21" long. As may be seen on image labelled balance-0, the balance is marked "20 4 EL CALDWELL". I believe the balance is 1/2" but have included images with rulers to assist the decision. The Swisco S385-21 or S380-21 seems right, but I am not completely sure which mine is.
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Bob from SWISCO responded:
October 22, 2023

Thanks for posting. You are correct, this looks to be either an S380-21 or S385-21. The difference between these two balances is the depth of the bottom nylon shoe, or its 'heel-to-toe' measurement. See the illustration below. Measure the depth of your balance's shoe to figure out which Series you need. In either case for a stamp option choose 2040.

Comparison of the S380 and S385 balance shoes.
Comparison of the S380 and S385 balance shoes.
21" Series 380 Channel Balance
21" Series 380 Channel Balance
S380-21
$9.38
21" Series 385 Channel Balance
21" Series 385 Channel Balance
S385-21
$9.38
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