A handy person from Connecticut, USA says:
September 11, 2016
Paul from SWISCO responded:
September 15, 2016
Thank you for your continued patience. The first and third photos show standard balance caps. The ones you picked out look correct; specifically, the combination would be our Series 351 channel balance. Your middle photo is peculiar, though. I'm not sure what this is. You mentioned the 18-108, which is a top sash guide, but these are screwed to the sash directly. Your picture shoes a shoe like the 15-002, which is at the bottom of the sash, instead. Plus, the guide (or whatever it is!) is screwed to the shoe itself. Can you go into more detail on what this part is? What function does it serve? Is it necessary for your balance to operate?