Two different things need to be kept apart here. An even reddish-brown sheen that shows up only against the light is normal and comes from the material itself: the black precious resin of the Meisterstück line is not completely opaque and lets light through with a wine-red cast. This is not a defect, and certainly not a sign of a fake.
Patchy, irregular discolouration at the lower end of the barrel, on the other hand, usually comes from ink residue. Ballpoint refills can leak under sharp changes in temperature and release small amounts of paste; this settles inside the barrel and at its end, where it forms a film that looks reddish in the light. Careful polishing with a soft cotton cloth, lightly dampened, will deal with it. Harsh cleaners, acetone and high-strength alcohol are to be avoided, as they leave the surface of the precious resin dull and can attack engravings. If the film keeps returning, the refill should be replaced and the pen no longer left lying in the sun or in a hot car.