I have an 80'
there is no Nissan badge on it, just DATSUN ( no "by Nissan" on it either ).
It may have started in 81 or 82.
But the 84 300zx was all Nissan badging and I do not think there was any Datsun on it anymore after that.
If you do find a 260 with a Nissan badge then someone just added it and it is not factory.
Kinda like what I did, added a nice Datsun badge from a 240 to my front bumper instead of a license plate - looks pretty good.
Ryan