Balances

I am trying to replace some window balances. The stamp on the balance reads 23DS 37 with a small stamp between it that looks like tsb mh. The balance is 24" long and 1/2" wide. I'm not sure what to get and the weight stamp. Worried to get the wrong thing cause the single hung non tilt windows are heavy at 50"x24" approximately. Any help you can give would be greatly appreciated, I have many to replace.