Mystery BSI channel counterbalance

Thanks for posting. This looks like either a S351-22 or S390-22. The only difference between these two balances is the 'depth' of the bottom nylon shoe, so compare both with your old hardware to see what matches best. Now, the stamp option you require deserves some clarification. Your stamp code of 21-4 conforms to our stamp option of 2140, which is for a window sash in the weight range of 15 through 23 lbs. However, you say your sash weighs 32 lbs. Did you ever have trouble keeping your windows open prior to the balances even breaking? This would be indicative of balances calibrated too weakly for your window sash's weight. If that's the case, and if your sash does indeed 32 lbs exactly, then you'd be better off with a stamp option of 2165, which is for a window sash in the weight range of 30 through 34 lbs. Let me know if you have any other questions.