Sometimes you can?t recognize grey market products, for example maybe Coke. If Coke just made one type of packaging and can for its Coke drink and shipped it all over the world, if would be very hard if not impossible to tell if it was a grey market product.
On the other hand, sometimes you can tell if a product is a grey market item. For example let us use Coke again. Say you bought a six pack of coke for a local store in your home town, but the Coke you bought didn?t have the normal packaging with it, and everything was printed in a foreign language, that is generally a pretty good indication that it is a grey market product. Not to say you couldn?t import things from a foreign country legally, like from monarch computer, that is not a grey market.
Another clue as to if something is a grey market item is if it is cheaper then it should be. And some items, like DVDs are only encoded to work in certain countries DVD players, in an effort to stop a grey market from happening.
I hope this helps at least somewhat, what I am saying is really just general information about grey markets, there is more too it, but at least it?s a start.