need help

I have a window which is about 30x36 and this is a picture of the coil springs without the covers on. The window, when open just quickly drops down. I am curious because it seems like the center coils were never working in unison with the outer coils. As in they never fastened or connected with the upper and lower spring. 

The coils on both the left side and the right side are are the same and in the same condition. Nothing is obviously broken but the window does not stay up. Please help me to get the replacement parts. I will provide the shipping address and payment method as soon as we can come up with the parts. Also please notice that the set screw in the second picture has the screw head teeth sheared off. Can you also advise me about that.

Hi Paul? thanks for looking into this. Just to tell you. The coils that I have were each individual in their own rectangular box so the coils had 2 cover plates. Your mounting frame for the double coils is a single piece and I hope that doesn't matter that it's slightly different. Because the current window is in use and it might become unruly if I disassemble the coil to find the stamp, would it be ok to go and weigh the sash on a scale? 

Also that little screw that we mentioned is inside the track and the screw head is sheared off. It will interfere with pulling out the parts. It looks like I may need to grind out the screw. I will try and turn it with needle nose pliers.

Hi again.
I am enclosing a few more pictures so that I can show you how the coil springs look with their covers on and how the hardware looks. Just to double check. Also I have weighed the window and it weighs almost exactly 30 pounds.