Yeah, that's why I avoid plated cases, with the exception of gold vermeil or plaque. I've often been tempted to buy something in PVD black, but I envision the stuff wearing off at the corners, so I don't.I have one of the Steinhart Big Flieger with the Unitas manual movement. Great watch per se but unfortunately in a sudden bought of bad taste back then I went with a PVD rose gold case. The color was quite nice but not durable at all. Now it lives in the dark corner of my watch case...
Does your Big Flieger have the big onion crown? Those are neat watches, and Unitas movements are pretty much bulletproof. Maybe you can have the remaining gold plating buffed off and polished.
I have several antique pocket watches in so-called "20-year" gold-filled cases; those show no signs of wear or brassing at all, which to me is remarkable.
More remarkably, I have several cheap, gold-finished deployant buckles that despite frequent use, show no wear at all. In fact, the deploys that have fared the worst have come from Rios in Germany, while the ones showing no wear come from the No-Name Buckle Works in China. Go figure.