Dan, I have a 100, 180 and the 200 foam blocks. The 100 makes quick work on tombacs. Just lay the block flat, place the tombac on the pad and using various degrees of pressure, just move the button around on the pad until you get that crud layer off. Then I might switch to the 180 or the 220 to get that dark layer of oxidation off. Same idea for coppers. Practice with a few toasted common coppers to get the feel of it. You can virtually remove just a few microns of crud at a time until you get to the level of "cleanliness" that you want. I have also used that method to get an ID on some totally toasted coppers. They looked completely blank but there is still some elevated surface area like the head or even the date that will come into view with some "polishing" with the foam blocks. Hey was that Liberty Cap #1,000 ???