Be aware that ANY machine, designed for pinhead sized nuggets, will easily find coins. I mean ... go figure, if they are sensitive enough to find grain of rice and pinhead sized nuggets, than a coin-sized object will be NO PROBLEM too, doh
But be aware, that if you have a strict "nugget machine", that ....... they might have p*ss-P**r discrimination. In other words, you might have no way to knock out iron (beyond the first couple of inches anyhow). Or if you have a machine that promises to be a cross-over (ie.: go back and forth between venues), then be aware: There are going to be compromises in each depth. Eg.: there will be better nugget machines, and there will be better coin machines.
Because, when you think of it, the goals of each venue are practically OPPOSED to each other. A nugget guy WANTS the "bells of notre dame" to ring over each staple, pushpin, speck, pinhead, etc... Whereas the coin/relic guy DOESN'T want to hear all that junk. Thus machines are designed, from the ground-up, for their purpose. So if a machine touts ability to go back and forth between both venues, then, ... rest assured: There are going to be compromises.