That was Eckhel's opinion, as I read somewhere in
Numiswiki or
Wikipedia or Lacus Curtius. So far I found nothing recent and archaeological to contradict opinions from
Eckhel to Nash's Pictorial Dictionary. As I wrote to a friend off line, it would take a round foundation of 3rd century date to say more, but so far I found only recycled citations, no archaeology. Apparently there was a Campus Martialis not identical to Campus
Martius, not that the epithet Martialis wouldn't be OK for either. Also, we seem to have no mention of that temple or
monopteros other than on those coins. That it looks like a
monopteros doesn't mean it didn't in reality have a cella wall, because of coins conventions (see
Price & Trell, who don't mention this one, however; see also Tameanko, but I didn't find it there). We don't even
know whether it was a permanent or temporary structure.
Pat L.