Window balance

Thanks for posting. Based on appearance, this might be 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 measurement from 'heel-to-toe'. See the illustration below for reference. In either case you have to choose a stamp option. Your old stamp of 28-6 seems to indicate you need a stamp option of 2860, which indicates a balance that can support a window sash in the weight range of 32 through 35 pounds. You can always weigh the sash to confirm this. Let me know if you have further questions.

Comparison of the S378, S380 and S385 balance shoes.