33' Window balance

Question

This is a 33' window balance with appears to be the numbers A3 240 23 and maybe a (d) at the end.

It could also read A8 240 23 and possibly the (d).

The widows are original and in a condo unit that was built sometime in the 80s.

Bob · Accepted Answer

Thanks for posting. I believe this is either an S390-33 or S351-33 Channel Balance. The only difference between these two balances is the depth of the bottom nylon shoe, or its 'heel-to-toe' measurement. See the diagram below for reference. Compare both balances with your old hardware to see what matches best. In either case, for a new stamp option choose 3240.

Comparison of the S351 and S390 balance shoes.