17 3 and 26 4 channel balances

I'm not sure. The stamps don't tell me what you have, unfortunately, they only indicate the spring strength calibration. To identify the right balance, you need to match up the nylon ends. I can see your bottom nylon end, which could be either our 15-004 or 15-005, but that's about all I can tell. I recommend looking over our selection of 1/2" wide non tilt window channel balances here. I'm confident one of these will work as a replacement, you just need to match up the right configuration of nylon ends.