21-1 stamp, need replacement part

Thanks for posting. This looks like either an S380-22 or S385-22 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 hardware to see what matches best. Let me know if neither is quite right. For a stamp option, choose 2110.

Comparison of the S380 and S385 balance shoes.