1950s era spiral channel balance - no names or markings noted on the existing hardware.

Hello,

I am looking to replace some spiral balances. This is the first window i am attempting; i will have two others (of a different size). The old window bottom sash is about 24" high (longest side). The old spiral balance mounting brackets were in the 5/16" wide channel in the sash, and there was 22" between brackets. The only 'external to the channel' part of the mounting was a bracket that extended about 1" above the channel/lower sash, where a screw secured it to the jamb just above the lower sash when the window was closed. This bracket can be seen in the second photo; i bent everything quite a bit when trying to remove it (not knowing exactly how to do that. The sash weighs about 9 lbs (without the old balances). Can you please advise replacement spiral balances and the hardware i will need to complete a replacement project?

Thanks very much! Al 

Thanks, Emily!
That looks promising. So, if i plan on purchasing two of the Series 500 balances and two of the 17-012 brackets, as this is my first balance replacement project, what else do i need? It seems like there should be two more brackets (or something) needed, and i would get the mounting screws from you as well. Can you advise on a 'complete package' of all parts? That would be fabulous...

Thanks!!
Al.