Hey Denis, since you’re from Belgium, I guess you can find the products we have in France. Try to get some Renov’pinceau. It’s very aggressive and will definitely remove the paint. I don’t think that there’s a slight chance you can save the original paint anyway, but at least, it will reveal the underlying details and won’t harm the metal.
But to be fair, I have another fear. The lack of details makes me think that indeed it was painted, but also that someone tried to clean it with sand paper, hence erasing the detail. I hope I’m wrong though.
EDIT: it’s an old product I had. Looks like environmental laws have sealed its fate as I can’t seem to find someone selling it. As every great product, the government is thinking instead of us and probably decided it was dangerous for us dumb humans. Now it’s probably been replaced by something ineffective, as usual.