By far the easiest way to confirm for yourself whether it is solid gold or not is to weigh it. Readers Digest did not make their fakes out of gold-plated tungsten and gold is more than double the density of any other yellowish metal, so unless the fakes are excessively thick, they will be much lighter than the regulation weight. Genuine ducats should weigh 3.49 grams. I own
two Readers Digest copies; they weigh 2.27 and 2.44 grams.
That being said, I'd be suspicious of yours. You say it's "not tarnished" but I see two dark streaks slashing across the emperor's neck and chest. That's not only tarnish (which I wouldn't expect to see on a real gold coin) but it's just the sort of damage pattern I'd expect to see on an RD coin that had been glued to a piece of cardboard.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis