Miller, get yourself some micro-fiber towels, after every time you roll, wipe the ball down. Then after your done keep one of those towels to clean the ball with any one of the methods mentioned above.. I use Neo-Tec Liquid Nitro,and Black Magic Particle cleaner.. I also have Simple green,but have not used it yet.. Main thing is wipe it down after every roll, this will help minimize the amount of oil to soak in the ball,and to take any other dirt off it for the next roll... Hope this helps..
GOOD LUCK
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Looks Like a Telefunken U-47
Jeff