Bob, your question has many facets. For starters, here's the obvious: yes gold jewelry reads in the various TID ranges that aluminum (tabs, slaw, foil, etc...) read in. There's no getting around that, no matter how well you "know your machine". If anyone tries to tell you they can tell the difference between gold and aluminum (by sounds, or programs, or whatever), then quickly take them out to junky blighted urban parks, turn them loose. See how much gold jewelry they get, while leaving aluminum behind
The next facet to you question: Yes, the parks are commonly hunted for coins/old silver only, and yes, people oftentime pass up foil, tabs, and so forth, ever since the creation of the first discriminators starting in the mid to late 1970s. So pity the poor fellow who tries to go to junky parks NOW, and hunt for gold jewelry
This depends on your geographic locale though, because some cities or parts of the USA might have had people who never high discriminated in their parks. But here where I'm at in CA, it's just the way it evolved.
And even though it's true, that people have "passed those gold rings", and even though it's true that if you dig enough junk in junky parks you will eventually find those gold rings, yet let's face it, it's simply not worth it. That's why people even from the beginning, chose to mine the parks for silver, and didn't bother going low disc.
Oh sure, you can try to be a "hero" if you want, but at some point, you're going to realize, it's not worth it. That's why I have to chuckle when I read on a forum where someone gives this prescription to finding gold rings: "turn down your disc, and dig all the aluminum". That is only a recipe for disaster, and no, it's not the full prescription.
The MUCH BIGGER part of the equation is
WHERE you hunt. Because I can give you junky parks, where your ratio would be 1000 to 1 !! Simply not worth it. I have done and seen actual studies done in junky blighted parks, where this ratio is no joke!
For starters, junky turf simply has a low ratio of gold jewelry, to begin with. And if you start adding factors in like trying to hunt around picnic tables areas, you will only compound the problem, because think of it: Anywhere people
eat, it's an automatic tabs from their soda's and foil from their sandwiches! And when you add in BBQ pits, presto, molten can slaw nuggets, and so forth! Contrast to athletic fields where there is NO picnicking/eating, and then your aluminum ratio goes down. Also the mere fact that it's athletics (especially rolicking frolicking tumble-over sports like soccer or volleyball, for instance), then the factors for jewelry loss go UP anyhow (as opposed to picnicking where all you're doing is sitting).
And better than ANY turf anywhere, is swimming beaches. Because the VERY NATURE of swimming is a natural recipe for jewelry loss: cool waters shrink fingers, people thrusting their hands in and out sand making sand castles, people putting slippery suntan lotion on, people frolicking about pitching frisbees and such, people laying in un-natural prone positions (on blankets, prone in the water and splashing water about). And my favorite: people taking off their jewelry for "safekeeping" when they've changed in to their bathing suits. Doh! Do you see why turf is such a lame 2nd behind turf?
So no: the recipe for finding gold jewelry is not to simply turn down the disc and dig junk till your arms fall off. You need to know where to go. And by "beaches" I don't mean only ocean beaches. Even beaches besides lakes with heavy beach-goer #s is going to be the same logic. And if you simply have no swim lakes in your area, then even volley-ball sand pits, sand wrestling pits, etc... are also going to be far and away superior to turf for jewelry. And think of it: sand is MUCH easier to dig in than turf anyhow. Doh!