Balancer

Thanks for writing in. Channel Balances generally aren't identified by stamps. The stamps on them just refer to their strength--that's what the '2020' on yours designates. Instead these balances are distinguished by the nylon attachments on both ends. In your case, you have either an S351-21 or S390-21 Channel Balance. The only difference between these two balances is the 'depth' of the bottom nylon shoe, or the 'heel-to-toe' measurement. See the diagram below for reference. Compare both with your old balances to see what matches best. In either case, for a stamp option choose 2020.

Comparison of the S351 and S390 balance shoes.