If you want to create faux artifacts and items that look real you need to duplicate the look of the genuine article. Luckily, we're able to draw on the knowledge and expertise of an entire profession dedicated to that very thing. I'm speaking, of course, of forgers.
As usual when I bring this subject up I'll point at that forgery is a scourge in the world of art and artifact collecting. That said, the people cranking out all those fakes have developed an incredible amount of technology and expertise that propmakers can draw on. Unfortunately, they're notoriously close-lipped about exactly how they accomplish their work The next best thing to consulting them directly is getting tips from the experts that help identify fakes.
Australian collector Louis McWhinnie has been kind enough to share some of his advice at his website. It's a good general introduction to the subject of artifact forgery and has some great insights. The first reaction to a lot of it will surely be "Authentic drill holes? Isn't that a bit over the top for a prop?" In most cases, yes, there's no doubt it's excessive. But it's also an incredibly immersive way to to demonstrate what that high-level Archeology skill is good for in a tabletop or live-action game: "Your examination reveals that the hole in the jade amulet has an odd hourglass shape, characteristic of being drilled with a friction drill in primitive conditions."