Unfortunately fake physical coins are extremely popular right now, they are all over localbitcoin and on the darknet for usually 40% of face value. I wouldn't buy any of them knowing they could easily be fake, I don't know what the coins are made of or anything but there is probably a way to tell for sure.
An actual casascius coin has the phrase CASASCIUS encircling the entire coin, in tiny letters, on the hologram. You can only see them with a microscope, or if you have reaaaaaally great eyes and catch it in the light right. It's quite beautiful, really.
I'm sure it is just as counterfeitable as the rest, but there's at least a chance that the production quality of the counterfeits isn't up to snuff and they skimped on this aspect. Something to keep in mind, anyway.
Honestly, I have seen 2 So far. BOTH ordered from darknet by a close friend (Why would you even be going there to buy those anyway?) Specifically S.R., in Fact. Crap seller with no feedback, I told him not to do it.
Both looked like trash, looks like it was made in China on the floor of a basement. He wasn't even mad they were so cheap, he should of known. I would compare it to the fake gameboys they make and market it the same or the fake Iphone's and MP3 players that look nothing like the original , they even name it something different like 'GameMaster' or 'WeeU", blatant and fake.
Fact is, I don't know what this kid is talking about. There not popular, there not going around. In fact they are ridiculously easy to spot. Mike C. has done an excellent job creating these, and I cannot wait for more to come!!
If he in fact has one that is fake and looks identical. Please, Pics or it didn't happen. For now everything is OKAY.
NOTE: Deal with coins daily, never came across one fake myself.