Constant force spring

Yep, these are also called coil balance. We can definitely help. Your shoe/housing looks like our 15-087, which itself is used with the Series 180 coil. Based on the stamp on your housing, I figure you need the S180-8, which supports 8 pounds per spring. Assuming you only have one spring on each side, then your sash is probably 16 pounds. You may want to double check that to be 100% sure.