Answer: The nude and the green polishes are fake. And while this means that the rest of the answers I will give you to the other questions are redundant, I shall still do so for the sake of comparison.
Answer: The green is fake.
Answer: The nude is fake!
So to summarize, these are the fakes:
I do have other fakes, I just chose the most convincing ones. The other fake I have has a white cap, and that's clearly not an OPI. Plus part of the cap is jacked up.
So how do you tell a fake?
Sometimes a fake OPI has a slightly slimmer, or fatter bottle shape compared to a real one. I don't have pictures of these, but if you look at other blogs, some do show that fake OPIs can be slimmer than real ones.
Shape of the base- Now look at the base of the polish in each bottle:
Which have weird shapes? Most prominently it is the silver and the pink polishes. These are real OPIs. The fake nude OPI polish has a pretty nice base actually. This shows that OPI has no quality control, which we all know already considering the 4 versions of My Private Jet and 2 versions of Not Like the Movies, and the list goes on.
Fake OPIs don't always use the same font as real ones.
The font on the nude polish is slightly larger than the font on the silver polish.
The font on the green polish is even smaller than the font on the nude polish. Both are fakes. OPI fonts are fairly standardized.
3. Symbols on the back of the polish?
These are both genuine OPIs:
But the pink one has 4 logos on the back, and the white one has 3. Now why the disparity, you might ask?
Well, the pink polish is ChicaGo Get a Manicure, a black label (ie. before 2006, not big three free). The white polish is Alpine Snow, a green label polish (I believe there's a black label Alpine Snow too).
The black label polish has 4 symbols. The green label polish has 3 symbols. BUT this is not conclusive. Go look at your stash! I have some black label polishes with 3 symbols and some with 4. Some green label polishes with 3 symbols, and some with 4 symbols! My Alpine Snow Matte (blue label) also has 4 symbols! UTTER MADNESS AND CONFUSION!
Thus we can only conclude that the number of symbols on the back of a polish is inconclusive.
Well this is probably the most conclusive of all evidence. Which is why I didn't show it to you for the poll. It would be a dead giveaway! For a very thorough explanation on this, please look at this blog post by Tim Tam, an online seller of nail polishes in Singapore.
But let me also present to you my take on it:
The first clue which tells you that the green polish is a fake OPI is the name. "An Affair in Red Square". Red is not green. If you know OPI and the (in)famous Suzi, they sometimes name their polishes with some sort of reference to the colour. "An Affair in Red Square" should be blatantly and obviously red. If you can't even tell that the polish should be red, then you better learn English well, because the Chinese merchants of these fake OPIs clearly don't.
Again, another indication. This particular shop I bought the fake polishes from in Beijing had all their polishes labelled "An Affair in Red Square" or "Alpine Snow". Even if you don't know OPI polish names nor do you have an OPI app on your iphone listing all their colours, "Alpine Snow" should indicate to you that the polish colour should be similar to snow, ie. white, gray, light glitter. I've only seen snow once in my life, in Shanghai during winter, and it's not a very clean country, so snow did turn gray after a few hours. Maybe snow isn't gray in your country, but wth it shouldn't be the colour of snow after someone has peed on it- beigy nudish yellowish.
BUT if you observe the pictures above carefully, you would have realized that the serial number on a real OPI is very BOLD compared to the faint fake OPI serial number.
For reference's sake, here is the green label OPI and the black label OPI: the serial numbers on both are BOLD, though of different sizes.
5. Serial number engraved on the bottle/handle?
I don't think this is a clear indication at all, despite what other bloggers have said. Because some of my OPIs have no serial number on them at all, but I did purchase them from proper sellers, either online or in stores here.
Furthermore, there is an etailer (ahem, transdesign/nailsupplies) notorious for shaving off the serial number. Something about OPI not wanting etailers to sell them, but I think this is not a clear indication of a fake/real OPI.
There is no fool proof way to tell a fake OPI from a real OPI, as these fake OPI merchants are getting smarter and smarter at what they do. If they can do it with Prada handbags, why not nail polish?
The only way which I have concluded so far is the font of the serial number on the label of the bottle, and as Tim Tam concluded, you should be able to peel off the top label to reveal another one on the bottom.
Other indications would be the shape of the bottle (fat/slim), funny handles, the names of the polishes, and if you know the polish well enough, the actual colour. My fake OPIs from China smell like death. Worse than kleancolors. They smell like wall paint and never dry without seche vite. That's another indication.
I also started writing this post because of Traci, from The Trace Face Philes, who came by a fake Mad As A Hatter polish. She emailed me to ask more about my fake OPIs, so I decided to do this since I was thinking about it for a while already. Anyway if you want to check the authenticity of the MAAH polish that you bought off ebay, refer to her post here.
I also don't profess to be an expert in knowing what's real or fake, but I do hope that this post can provide a little guidance!