The Dos Peso is a pretty small coin. I have this exact coin and this one looks the same not as sharply struck as mine. Even if it was a jewelers copy most are still 22k. If you are getting it for close to melt you are not looking at very much money. I would think it would be pretty hard to tell unless it was in hand.
it is real and do not pay much for it...look on ebay, i have one that i got in mexico, some mexican banks actually still have them for sale at spot prices. these are not at all rare.
Problem being it's a lot easier to fake a certification than an object. I consider certifications to be fairly useless unless a person runs it down as to contacting the certifier. Even then all they might learn is they still might not know if the certificate is fake.
I suspect most times a buyer will see the certificate and make a bunch of assumptions such as "It must be real because it has this impressive certification." Without investigating, you'll never know.
Watching Pawn Stars, it's staggering how many fakes are made of just about anything. Once they were testing a gold bar. their concerns were if the bar was hollowed out and refilled with tungsten. Looking on the Periodic Table the two are almost the same weight.
Guess I'll just resign myself to living with events like fake news and alt-facts knowing nothing can be perceived as real or at face value. If it has value it will be counterfeited.