Cant tell which series to buy

Hello,

We can't be sure with the balance still installed, but the S351-13, with a 15-002 bottom attachment, or the S390-13, with a 15-001 bottom attachment, would be a good place to start. 

 I don't see a stamp code on your balance channel. If there is no stamp, you'll need to weigh the sash and follow the chart under the balance product description to choose the correct spring strength option for your replacement balances. Thank you!

How to measure the length of the Series 390 channel balance.

Comparison of the S351 and S390 balance shoes.