2930 bs window balance

Thanks for posting. This looks like either an S351-30 or 390-30 Channel Balance. The only difference between these two balances is the 'depth' of the bottom nylon shoe, or 'heel-to-toe' measurement. See below. Measure your old balance's shoe depth to see what matches best. For a stamp option choose 2930.

Comparison of the S351 and S390 balance shoes.