Here we have one of the stranger innovations in shaving technology. This is a Pomco slant head razor. We think it's pre-war since it's been made in Germany. Hoffritz of Germany would go on to make this type of razor famous after the war, but Pomco had the patent in 1937. The head is intentionally twisted to offer many different shaving angles from the same blade.
I'm not positive, but the black appears to be plate loss and not a stain. Something more than our standard "clean and sanitize" process would help determine this. The plating on the head is still very good. Even with the odd twist, this razor uses standard Gillette style blades which are available in a variety of brands.
Plenty good enough to use, or priced cheap enough for a replate project. Interesting and somewhat rare razor.