Looks like a brake proportioning valve, if not the same one, then very similar to the one shown in this ebay listing
https://www.ebay.com/itm/47150-12270-To ... SwkNRd3sIy
not sure why one would be needed with ABS, the internet says those things are used to prevent the rear brakes from locking up in heavy braking. I have no idea how they work. Might be easier/cheaper for the factory to put them on all cars, and not bother going with a different set up on those cars that get ABS