Does anyone know what this is? It weighs 7.9 grams and has a diameter of 25.9mm and thickness of 2.4mm.
I don't recognize it. It has a vaguely Eastern or possibly Danubian Celtic appearance, but the texture looks like it might be cast.
It's some sort of cast fantasy or imitation. The second image is appears to be patterned after a Philip II tetradrachm. You can make out what seems to be ΦΙΛιΠ and the horseman is carrying a palm. Here's an example: Philip II of Macedon did issue a ton of small bronze coins with similar iconography (reverse). There are many Celtic imitations of Philip II coins. Could your item be an ancient Celtic coin? I don't know but whatever it is looks cast.
Here are my Celtic Imitative Drachms for comparison...from trusted well known Auction / Dealers. I do not make any speculation on authenticity from pics. I am not an authority. If I saw the OP pics in an auction or online, I would personally move to the next choice. Celt Imit Philip II 2nd C BCE AR Drachm Zeus Horse pellet-in-annulet above Kugelwange type- Danube Valley - Kostial 508 OTA 204 Celtic Imitation Philip II 2nd C BCE AR Drachm Kugelwange type- Danube Valley -
It looks like a man riding West on horseback with his wife and two kids, then on the other side, he's riding back East...alone.
It is a modern cast fantasy (fake) with only a slight resemblance to the original ancient Greek coin of Philip II. It is not Celtic. It is not ancient.