The end of the spiral is missing (broken off). I believe there were two holes drilled in the flat end of the spiral. The part that attached the drilled holes to the bottom of the window is also missing, but from marks on the window, I believe it was a right angle piece of metal that was attached to the flat part of the spiral and then to the bottom of the window via the square drive machine screw that holds the bottom of the window to the side of the window.
I have enclosed photos of one of the windows and a detailed photo of the bottom corner of the window with the square drive screw. If there is no stock piece of metal that will attach the bottom of the spiral via the two holes to the to square drive screw on the bottom of the window, I could probably fabricate such a piece and attach it to the two holes in the bottom of the spiral via rivets or vey short machine screws and locking nuts.
As long as the sash balance is the right diameter and length and can hold up the window, I can probably find a way to attach it to the window, which will be better than sticks propping the window open, which is what I have to do now.
Thanks,
Dennis J. Finn