27 3 Window balancers

Thanks for writing in. This looks like either a S390-27 or S351-27 S390-28 or S351-28. 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. You will need a stamp option of 2730. 

The stamp option is more or less the stamp code printed on the balance's metal channel. This indicates the calibration of the balance spring in the balance. Your balance has 27 3 stamped on the channel. This conforms to our stamp option of 2730, which you can pick on the balance shop page. 

Hey, hopefully I can help. I think there was an error here. If your balance is stamped "27 3," then the length of your metal channel should be 28", not 27". Looking at your photos, this appears to be the case. I'm certain Bob just made a typo in his original request. Sorry about that!