29-9 balance

Hello and welcome back! 

With this combination of fittings, you could have either an S380-30 or S385-30 channel balance. You’ll need to measure as shown below. The Series 380 has a 1" bottom fitting, and the Series 385 has a 1-3/32" fitting. Your "29 9" stamp is outdated, though. You'll need to weigh your sash and refer to the chart under the product description on the S380 and S385 store pages to determine the appropriate spring strength option for your balance. 

Comparison of the S378, S380 and S385 balance shoes.

In that case, you will need the S380-30 channel balance. If your sash weighs exactly 35 pounds, you have two choices: either the 2960 option, which supports a sash weighing 32 to 35 lbs or the 2965 option, which supports a sash weighing 35 to 39 lbs. Either option should be fine, as long as the exact sash weight is 35 pounds. The decision is ultimately yours.