need to determine spring weight for S385-36 channel balance (stamp says "35DS 55L")

A handy person from FL says:
May 15, 2020
Subject line says it all. These are heavy impact windows. Does the "55L" mean I need a 55 lb spring weight?
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Bob from SWISCO responded:
May 18, 2020

Thanks for posting. Yes, that means a pair these balances with that stamp code will support a 55 lb lower sash. We can supply these balances for you, but they have to be custom made due to their unique design. I am sending you an email with a custom link to order a pair of 36" Series 385 balances, with a stamp code of 35DS55L. Let me know if you have any other questions prior to ordering.  
36" Series 385 Channel Balance
36" Series 385 Channel Balance
S385-36
$12.27
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