Which OS Bernina foot is this?
 

Newly acquired Bernina 830, this is one of the feet that came with it. no number is present.
[ATTACH=CONFIG]546978[/ATTACH]

looks like an invisible zipper foot. They were normally sold by teh company making the zippers, and it came with several colors of plastic pieces to use on different machines.

You slide the foot over and the teeth of the zipper fits into one of the groves (depending on side) and it unrolls it just a bit so you can stitch right up next to the teeth.

Since I collect vintage machines and attachments, I've got a bunch of these now.

Back when I sewed bridesmaid dresses - I put in a lot of invisible zippers.

Thanks so much, I tried Googling, not much luck w/out a number.
The previous owner seems to have been a seamstress, not a quilter...

That is what I also thought it was too. Keep the upper part because that will allow you to use on any generic foot you might want to use.

Sweet! Thank you, I will, thanks for the info!

Yeah, the upper part is an "adapter" and can be used on the generic feet. I have 2-3 of these collected over the years.