29 9 hw cmc 11

Thanks for posting. This looks like either an S380-30 or S385-30 Channel Balance. The only difference between these two balances is the depth of the bottom nylon shoe, or the measurement from 'heel' to 'toe'. See the diagram below for reference. Compare both with your old hardware to see what matches best.

Comparison of the S380 and S385 balance shoes.

You then need to choose a stamp option, which denotes the strength of the balance. Your old stamp of 29-9 is from a rating system we do not use. To know what stamp option to pick, weigh your window sash. You can then match that exact weight with one of the weight ranges listed alongside each stamp option under the product description of either the S380-30 or S385-30 shop page.