Yup. I think they were put on that way.

The first time I knocked one off I thought I would have to take a trip to the welding shop. Then I noticed there were no weld marks on the parts.

There was a clear indication of where the weights had been on the shaft. They were just cleaner.

And if they had been welded on they would not have just dropped off when I banged the driveshaft around.

So I tried the superglue with a C-clamp to hold it overnight. I never had one come off.