Thankyou all for your replies and input. I had never heard of a magnetic tumbler before PTsideshow posted this thread, so I am curious as to how this works. So, the small magnetic "pins" are swirled about by the magnets, causing them to abrade or polish the pieces of non magnetic pieces in the bowl. I would love to experiment with this this as I have lots of motors and magnets. But before I shell out money for these pins I am thinking I could use some steel 'shot' instead. I was thinking of shot used for shot blasting, or even shot used in shot gun shells. Just an idea since I could probably buy it locally.
After doing some Googleing I found that shot for shot peening is available in a lot of different sizes and 'textures', from smooth to coarse. But only available in 50 pound bags.
One other "what if" that came to mind.....What if I wanted to polish a lot of magnetic pieces, and I used a non magnetic media, such as ceramic balls. Theoretically, the magnetic pieces would swirl about in the media which would not move.
I'm only guessing, so I will build a small version and report back with my findings. Please don't hold your breath waiting for my results, my 'things to do ' list is 6543457 pages long.