Most of the countermarks shown here are indistinguishable to me except the one with the tripod (is that an altar?). I don't have any countermarks on ancients. Has anyone ever used silly putty to get a relief impression? Maybe they could be more clearly seen.
The obverse of this Seleucid coin has Apollo and countermark of Tyche or Artemis . The reverse shows a Palm tree and some lettering on both sides. I made sure that the coin was struck in Tyre - Phoenicia. Couldn't find a more elaborated description.
I'll have to take your word on that being a Seleucid coin . Interesting. Why would the Selucids counterstamp one of their own coins??
It's an Antiochus III Apollo/Elephant type IIRC. As to the second question I believe it had something to do with some sort of military campaign in Ecbatana but I can't find my notes on the subject so that could be totally incorrect.
Maybe they assigned the coin/denomination a new value and indicated that with a countermark? Surely someone here has a ready explanation and links to various references.