I can't say that I've ever paid good money for a parts speedometer unless it said Stingray on the face though. The cables are most always too short on exercisers, but the drive can be used on anything 20".
Well, if it says "Sting-Ray" on the face, it's not a parts speedometer.

Yeah, I know what you mean: the Exerciser speedos are a good source of restoration parts, especially the non-rusted bezels and unbleached, bright-orange pointers, though I always keep a couple of un-parted, rebuilt Exerciser speedos on-hand for people who want to get their Exercisers back in order for the winter.
The earliest Exercisers used the original heart-shaped Huret casings and a 0-60 MPH dial, such as is seen on the white one in the Facebook listing (or you could buy a standard 1967 XR-2 Exerciser, which apparently had no speedometer at all).
The heart-shaped speedo head soon changed to the standard Schwinn squarish dial and case when Huret became Schwinn's newest speedometer supplier beginning in 1967, although the Exerciser cases were always a gray Hammertone texture finish rather than chrome, since the head was panel-mounted and the back case would not be visible. The first Schwinn-branded speedo in the Exerciser was a 0-60 MPH unit, same range as the previous Huret unit, but common sense finally prevailed a bit later, and they backed down to a black-faced 0-40 MPH unit, so that you could get some kind of positive feedback in terms of a nice high speed reading on the dial without having to stand on the pedals.
I once swapped a 0-40 MPH Deluxe dual-scale head (one of those with the MPH dial stamped in gold) into an Exerciser case for a gentleman who wanted to add a little more sparkle to his Exerciser. Hey, whatever inspires you to keep exercising is a good thing.