Looking for channel balances for 60-80+ years old aluminum windows in Philly

A home owner from Philadelphia says:

I am looking for channel balances for 60-80+ years old aluminum windows in Philly. I just double-checked , house is built in 1974. These are duplex homes, outside is brick, all windows are original aluminum. This specific window has a sash of 22" x 24 1/8".

Thinking of this product (and it looks similar to existing):
22" Series 385 Channel Balance
Product Code: S385-22

I can't weight it, I need to spend an hour driving to the place with weights. Do you think it is 2110 or 2120?

Attached is the best picture I have, with cellphone, it's dark.

Profile picture of Tom
Tom from SWISCO responded:
Thanks for posting, Alex! I'm afraid I can't say for sure how heavy the window sashes are. It depends on many factors, and judging by the age of your house I don't think we can reliably estimate the weight. There are just too many little details that could alter it, and balances are fairly precise systems. It's important you only get the option that matches your weight; no more, no less. I'm sorry we cannot offer you an easy answer, but the only way to know for sure is to weigh the sash.
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