Window Block and Tackle

Question

I have some Block and Tackle I need replaced. Best I can make out is they are BSI 21 12 from the imprint. I do however think that these are not the correct size for these windows as they are quite heavy. The window measures 4' wide by around 22" height. I have attached 5 pictures for reference. Thanks.

Bob · Accepted Answer

This looks like either an S351-22 or S390-22. The only difference between these two balances is the bottom nylon shoe depth, so compare both with your old hardware to see what matches best. Your stamp code of 21-12 is a little unusual. I recommend obtaining the exact window sash weight. You can then match that exact weight with one of the weight ranges listed alongside each stamp option on the shop page.