Sash window spring

Thanks for writing in. I believe this is either an S380-29 or S385-29 Channel Balance. The only difference between these two balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement; compare both with your old hardware to see what matches best. See the diagram below for reference.

Comparison of the S378, S380 and S385 balance shoes.

You'll then have to choose a stamp option, which designates the balance's strength. Your old balance's stamp is admittedly tough to read--the '60' might be from a stamp that originally read '2860', which would indicate the balance is designed to support a window sash in the weight range of 32 through 35 pounds. I would weigh the window sash, on a bathroom scale, just to be safe. Let me know if you have further questions.