These things are used for all sorts of stuff, not just slot cars...and they can be had for a buck or two.
This one had a freakish wind using wire that measured slightly thicker than #27, undoubtedly a metric, and only 32 turns. Maybe for some really fast car mirrors or something.
While the magnets are very strong, they're also long and there's no reason to go through all the pain of cutting them down when there are plenty around the right length. With some cutting and nibbling, flattening and sanding (*all five sides), and finish milling to length...oh and a little paint and a couple of bearings, things are looking a lot more slot-car-motor-y. Being actual "fk" size, the end bell needed a bit of turning-down to fit, so I dug out the fixture I made to do that.
Here's some recent holiday family photos taken just this past Christmas, when "Uncle Green" was over for dinner.