Identification help




Hello there. This looks like it might be either a Series 161 Coil Balance system, which is 9/16" thick, or a Series 210, which is 7/8" thick. Yu'll need to remove the old coil balance shoe and measure the thickness to confirm. If there's no cutout on the window jamb, you can make one yourself. The video below shows how to do it for a similar coil balance assembly.
You have to choose a spring weight for the replacement system. Judging from the stamp on your balance shoe, you'll need either a '6' or a '9' pound system. Unfortunately we can't say for sure which you need! If in doubt, weigh the window sash the coil balances support. Give us that exact weight and we can work out what you need.

I weighed the window sash and it came in just under 9lbs and my coil balances measure 7/8"
It also appears that the coils have 6D stamped on them



If your shoes are stamped with 6D, then they should be holding 6 pounds each. That means you have 12 pounds of total support.
That's quite strong for a sash that's only under 9 pounds in weight. Have you ever found that the window was difficult to close before? It would have taken quite a bit of extra pressure just to get the window down.
Either way, we don't sell anything that perfectly covers 9 pounds of support, but our S210-04 is 7/8" thick and a pair carries 7 through 8.99 pounds. That should be sufficient for your application.