Connected flexible 2 x 2 white plates - what set? I'm going through my old Lego collection and trying to identify the original sets they're from. The bulk of the Lego is from the 70s and 80s.

I have a piece that is two white 2 x 2 plates joined together by a thin cord. I seem to remember it joined a car to a cart or something like that, but I can't find the part in any of the sites I've looked.

Can anyone help me with this piece (either how to properly describe it when searching catalogues or possible sets it may be from).
That's an old 650 Hinge Coupling Nylon - Two Connected 2 x 2 Plates from the 60s.



It only ever came in 20 sets, but it's typically clear. It's listed as a possible alternate for the following set, but it's possible other sets could have had it as an alternate too.

901-2 2 Large Wheels with Accessories