A sure telltale is laser writing. You can tell on their second example - the writing is sharp and perfect. Often the logo is not quite solid color, and you can see it has lines from the laser in it. The color of laser-'printed' text is also typical.

The originals often have pretty bad markings on them, actually. Off-center, not aligned, not evenly printed. Too perfect is suspicious.

Also look at the pins. Sometimes they dip the feet into solder to make them look unscratched and shiny. I have avoided buying 'New Old Stock' ICs because I could tell the pins had solder on them.

A couple of times I found the IC was of the type advertised (after I removed the paint). I guess they just added a fresh coat of paint to make them look new!