Question About Color

I've been digging through some of my long term unidentified coins this afternoon and there are a couple that always catch my eye. They're in rough condition but they have a different color than I'm used to seeing. They're smallish but chunky. Here's an example.



5.7 g, 16 mm

I think it may be Macedonian or Thracian. It appears to have a prancing horse on the reverse and has a bust (Apollo?) on the obverse. I don't expect to attribute it really, but it has a much... shinier? color than other bronze coins I have. Did they treat some coins in a different way to get that effect? It seems to have worn off some on the obverse so I thought maybe they did something similar to how some later Roman coins were silvered, but with a different composition of bronze or something.