.... Gold is often so similar-to-slaw sounding, you don't get as much advantage with the nox for that.
The same is true for every machine. Since gold jewelry comes in so-many-shapes, it can mimic can slaw. Even concise rings can have heavy sides "crowns" (bigger ends), that .... they can sound different, depending on the sweep direction. As opposed to coins which are perfectly uniform in shape/dimensions.
Add another annoyance : Rings with a "crown" will tend to eventually be on edge, with the heavy side down, in un-disturbed turf. The reason I know this is that a friend of mine took a year long study of a certain park in San Jose. He'd pulled a lot of silver and wheaties out of a certain section in the prior years, but had always gone high disc.
One day he decided he must be leaving a lot of nickels and gold behind, so he decided to do an experiment : He went into relic mind-set (ie.: dig anything/all conductors). He gridded off a big area, and .... for months and months , anytime he hunted there, he purposefully dug every single thing. Eg.: even down to foil, etc... And kept careful records of depth, ID, etc... Even to the point of digging slowly to ascertain accurate depths, etc....
And yes, he did dig some gold rings with this strip-mine method. And he noticed that when any of them had a "crown" (a heavy side), that they were always heavy-side down. And as you can imagine, that immediately takes away an "round" sound they might have had.
In the end, btw, after thousands of trash items and a meager handful of worthless orange buffalos and Vs, and perhaps a dozen gold items, he concluded it simply isn't worth it to strip-mine junky turf for nickels and gold. He realized he could simply drive over the hill to Santa Cruz beaches, and have a much better odds at gold rings, w/o the punishment, haha