Hmm although not familiar with the GB signal response I'd say your more than a good chance if you can repeat a signal from a gold ring, I concur with GP copper would ring up a higher conductivity ID, secretly I test mine using a test kit picked up from the prospecting shop (yellow and green lid bottles) very cheap and accurate, despite needing a little gold dust extracted from the source piece. Now the secret is out I can say my gold finds don't make it public, it's a small world and I turn the Rings in so I figure finders keepers. If you decide to sell try the regular gold buyers, and set that as the reserve price can't lose. The gold content will be important to a potential buyer. If that turns out to be plated I'd be very interested to see what it was.