There's a place near me that has a bunch of Atari games sitting against a wall. I can't tell which Atari they are for, or even if they're for the same system. Some are standard box shaped, some have slanted tops, and some have special labels. I know there were no manufacturing standards, and companies could make their own cartridges, correct? So those may all be different 2600 or 5200 games? How can I tell?