A contractor from Philadelphia says:
October 11, 2016
Looking for the pieces that attach the sill to the spiral balance. The balances look fine but the sash is missing the connectors
Paul from SWISCO responded:
October 14, 2016
Thanks for posting. I could be wrong, but I believe you're looking for the pivot bar. Is it missing on both sides? Could you have an identical window in the house that still has this hardware installed? It's really tough to say what can work without seeing what was originally there. It may be something like our 26-330 housing and 26-040 pivot bar, but I'm not sure.