I'm assembling my starter right now and I'm using a wrecking yard C3 nose, newer barrel, old plunger cover, non-pop riveted brush holder and old band.
My starter should be, at latest, an early January 1967 date so I feel a stamp would be proper.
I could not find a barrel that didn't have a D2 or later number so I took the best one (electrically speaking), and sanded the area where the numbers were and used body filler to fill in the engineering numbers.
However, this left the barrel shiny in that area.
The fix was to apply a few coats of black paint, wrap the area in 100 grit paper and lightly tap on the paper with a flat body hammer.
Blow off the "crumbs", apply a light misting of paint and the area now looks like the rest of starter.