Thank you for your answer.
Maybe these parts are made for consumer products, cheaper but with less quality screening?
I don't know. But the fact, that this chip simply does not not exist in the Motorola databooks let me believe that this was a kind of custom manufactoring, cheaper, but mayby slightly out of the standard specifications for a LM324, so it could not be sold as a LM324. But good enough for consumer stuff.
The most annoying thing is, that I have no idea how this part came in my stock....