Merkur sold their (own and rebranded) silverhandled razors with a thin layer of varnish so it wouldn't oxidize. With use, that would rub of so you'd get dark/black spots from worn varnish, with heavy use worn silver, or oxidation. The oxidation you can counter with the alufoil/bakingsoda trick, but I'm not sure what that would do with the rest of the varnish, which on your razor still seems to be in real good condition.
Looking at the offerings of Pomco and Hoffritz, Hoffritz always stuck to the Merkur-variations of razors, where Pomco experimented with other types as well, see Pomcomatic or Lady Pomco. This model I've never seen as a Merkur, which is why I think it's a late (their experimenting took place 60s-70s) model Pomco and not a Hoffritz. Not an absolute certainty though.