CertainTeed balance systems tend to use the 15-192 Pivot Shoe, along with the Series 170 and Series 171 Coil Balances. The video below goes into more detail. To know what spring weights you'd need, we'll need the exact weight of the window sash. Give us that exact weight and we can calculate what you need.
If the sash weighs exactly 25 lbs, one of our S170-406 6 lb springs and one of our S171-406 6 lb springs on both sides of the sash should work. This equals 12 lbs of support on either side of the sash, for a total of 24 lbs of support overall--so long as the overall support falls within one pound of the exact sash weight, this should work for you. I would, of course, remove the components and compare with what I've listed on this page just to be absolutely certain this system matches what you need.