Hi Old Guy,
I just had a look at a pair of c.2011 P-90's I bought a few years ago. I was a bit puzzled at first but the guy seemed very trustworthy, and searching online for images seemed to confirm that they were the genuine article. As you say, no markings of any kind. The brass baseplate has the corners sheared off on a 45 degree angle, about 1/4" across the flat. The wires (braided shielded and a small white PVC insulated wire) pass through a 1/4" hole in the corner and solder to a tag held by a phillips screw between the two end polepiece screws. There is another phillips screw opposite, and two unused holes between the B and G and between the A and D polepieces. The coil is bound with black tape and appears to be wax-potted.
It is curious that there are no markings; they look a bit like cheap generic pickups. As far as I know though, they are original equipment. I haven't looked at recent Gibson aftermarket P-90's so I don't know how they compare.