The best is certainly this one, which looks to be some sort of Augustus undertype. The same set of countermarks is known to appear on coins of Augustus from Ephesus, so that could be the case here as well. The countermarks on the obverse are TICA, AVG and, although indistinct on my example, a helmet. The most interesting one, however, is the reverse, which shows a dolphin right within an incuse rectangle, with a dot within circle on the bottom left. It's a very attractive and interesting countermark to me, even if the dolphin's head didn't quite strike. The other countermark appears on what I suspect may be an issue of Tiberius from Carthago Nova (the shape of the busts is similar, and I can just make out the letters 'IN' on the bottom right side of the reverse) and has a countermark which looks, to my eyes at least, to be a helmeted face looking left within an incuse circle. Could this be Mars or Minerva, or is it something more generic? At any rate, it's soaking in distilled water at the moment to deal with the tiny patches of bronze disease on the reverse. If you've seen (or own) any of these countermarks or their undertypes, post them here, along with any other countermarks you count as interesting.