30" window balance

Greetings! Thanks for sending us over some photos of your balance. We were able to narrow it down to two series. To determine which of the two is right for you, you'll have to measure the bottom balance shoe depth. If it is 1'', you'll need the S380-29, but if the shoe's depth is 1-3/32'', you'll need our S385-29 balance. The spring weight for either balance will be the 2820 option, as determined by your 28B stamp. Let us know how this works out for you!