Balancer

Hi there. This looks like either an S795-26 or S795-27 to me; to know which length you need, measure out the metal channel. To know what stamp option to select (which determines the strength of the balance), your old one of 26-5 is a little weird, so I advise you obtain the exact weight of the window sash. You can then match that exact weight with one of the weight ranges listed alongside each stamp option on the balance's shop page.

You seem to indicate that the balance screws in at the top of the window track. If so, great; the only remaining matter is to determine the T-Lock Shoe you need. The Series 795 comes with the 15-195 attached by default. This has a 'closed cam' that you can't see through the back of. There's another shoe, the 15-195B, where the cam is open and you can see through the back of it. I can't tell from your photos which you have, so compare and see. If you need the 15-195B Open Cam shoe, this is sold separately; but it's easy to swap it out with the default shoe. See the video below. 

A screw like our 33-016 should do the trick, though this sometimes can depend on the exact nature of your window track, so if you're really uncertain consult a local hardware store. Also, to be clear, your old balances attached to the top of the window track with a screw clip and not a hook like the 15-198, right? Please confirm. I agree, the 15-195B Shoe looks correct. Let me know if you have any further questions.