John, I have two sets of "Morris Mags" that look similar to your picture. One st has a 14mm front axle bearing set and the other is the later 17mm bearing set. Both sets have front dual disc and a rear disc brake set up. They look very close, I don't know a lot about the '70s stuff but both cast sets came from R 90S bikes.
Hey Jeff, thanks for the note. You see the Lester wheels quite often, but the Morris wheels that you have don’t show up quite as often. I remember Butler & Smith offered them in their accessory catalog. Share some photos if you don’t mind.
They look like Morris mags just going by the rear disc brake set up. I will take some time in the next few days to dig out my two sets of Morris mags to confirm as well as the rear caliper set up for each. Its funny that I have two different rear caliper types for these wheels.