Reminds me of how, back in the day, software would look for the letters "IBM" at a specific ROM address (it was in their copyright message) in order to identify the video card as a VGA card (or maybe it was back in the EGA days, can't remember). One of the clever clone card manufactures put in the ROM "There are various pieces of software that expect the letters IBM to appear here".

Or how a game would make you answer a question that you would only know know if you had the manual to accompany the game.

"What is the fourth word from the second paragraph on page 13?"

Presumably you didn't have access to a copy machine if you were stealing software back then...

IIRC some games came with a data booklet printed in black on very dark brown, or similar, to foil potential photocopying.

There were still boatloads of counterfeit GBA games, particularly Pokemon. If you bought any used Pokemon games, odds are very good they were counterfeit.

That's an open-and-shut case (provided they catch the bootleggers). This was meant more to (theoretically) stymie something like Tengen's 3rd party NES carts. Nintendo wants a cut on all the games that play on its consoles.