Double coil I can't find similar

Hey Paul. This looks like an older version of the Series 140. What's nice about this particular system is they come as one package, with the pivot shoe, coil balances, and housing all ready to go. That '8' on your old balance's housing might mean you need an S140-8 8 lb system; but weigh your window sash to be safe. If it weighs 16 lbs, this confirms you'd need two of these 8 lb systems on either side of the sash.