So -- the older it is, the more likely that it will suffer from
being disassembled.

Now -- if the magnet and carrier remain in contact with the pole
pieces, you probably won't hurt anything. But if you separate them (a
major struggle with a good one), you will lose field strength -- unless
they have started making them with the rare earth magnets. (The same
applies to the dial indicator holders and to stepper motors too, FWIW. :-)

Good Luck,
DoN.

My guess is that the chuck is from the mid 60s since that's about the
age of the surface grinder.

I'm not entirely sure what you mean in your second paragraph. My
hunch is that I should turn the chuck "on" and then try to disassemble
it. That way the magnets will be attached or close to whatever should
be keeping them magnetized.

......OR...

Do you mean that you can open it in the "off" position, but just don't
move the magnets off of whatever they're attached to in the bottom
half of the magnetic chuck?

RWL