Correction to what I said yesterday... I do not believe the transistors were sanded after all. I think maybe the primer etched the face of the transistor slightly and made the part number harder to see.
Not sure what those turned out to be in that thread.
Aion mentions in the Oberon (Bosstone) doc:
The transistors used in the original Bosstone had a nominal hFE of around 135. This is lower than the
typical 2N3904, but right in the sweet spot for the 2N3903.