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

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.