Cool. I haven't thought much about buying one of these, but they are really nice. Btw, regarding the marble top, I had heard that from a few people, so not just one, and I have seen old NCR machines with hundreds of tiny little chips in the marble, so I do believe its true. Actually the marble is almost always needing replaced on these machines, since the old ones are always marked up that way. It works too! Drop a silver and a clad quarter on there, you will hear the difference.
You will notice there is a chip off it's marble on the extreme left side in the first photograph. I have located a firm in New York that claims to get their marble from the same quarry in Italy that NCR did. I am buying a replacement top through them. It's as close as you can get to original issue and parts.
We had a restored version of the small register at the pizza parlor I used to work at. Really neat item. And I have always heard that same explanation for the marble top. Drop the gold and silver coins on it to listen for counterfeits.