Bard,
These are the obsolete Timken part numbers for the Douglas wheel bearings as used on the 1930s models. The 00152x is the cup, as you noted, and has an outer diameter of 1.4375". The other are the cone being 00080x and 00081x (pretty sure there are three zeros), though I forget what the difference is between the two. I have seen both, and one would certainly be 0.500" bore. The other might be 0.4375" bore, which Douglas did use on the 350cc models, and for the front axle of some of the big twin models. Last time I was able to buy some of the 00152x was 1987. These cups and cone are very difficult to find now. Both cones use the same cup.
Original SKF numbers would be W5700 for the 7/16" bore and W5840 for the 1/2" bore.
I have no idea what on a Jaguar might be using these small taper roller bearings, but I am pretty sure it would not be a wheel bearing!
-Doug