coil balance

Thanks for writing in! This window appears to use the 15-087 Coil Housing Pivot with the 15-086 Tandem Coil Housing attached to the top of it. Both of these do use the Series 180 Coil Balance. 

That said, to determine the exact coil each of these housings would need, you'll need to look for any stamps/markings on the coil. For example, the coil in the photos appears to be marked with a 6, so you would need the S180-06.