Channel balance replacement

Thanks for writing in. This looks like either S380-30 or an S385-30. The only difference between these two balances is the 'depth' of the bottom nylon shoe, so compare both with your old hardware to see what matches best. Your stamp code of 29 9 is from an older ratings system we don't use. Since you've helpfully provided the weight of your window sash at 31 lbs, this means you should be okay with a stamp option of 2950, which is for a window sash that weighs 28 through 32 lbs.