Thanks Gav for the advise... I used one at Marks the other day for a pinball I'm restoring. Left the tumbler on for 2 days straight 'cos the metal parts were pretty rusty. I was impressed on how well they came up! Hence why I bought one for myself... Yep, nothing beats a hands free polish!

Got another pinball here that's also pretty badly rusted / corroded, so my new tumbler will get a workout on those parts