A quick learner from Bonita Springs Fl says:
March 4, 2014
Both channel balances are broken the springs are pulled away from the fixed support and the pulley. The window is 50" wide by 36" high. I have attached pictures of the balances. The channel is 35"long 1/2" wide and 9/16" deep. The spring is 16 1/2' long. It appears to be similar to your series 380 or 385. We bought the house used, and the window never operated right, it opened ok but was hard to close.
Tom from SWISCO responded:
March 6, 2014
Hey, thanks for posting. Like you said, this is either our Series 380 or our Series 385 balances.
Now, as you can see, there is only one difference between these two Series, and that is their bottom shoe. The Series 380 uses the 15-005 while the Series 385 uses the 15-004. I can't quite tell what you have based on your pictures, though. Please carefully compare their dimensions to your own hardware and see which is a better match.