I'm not sure there's any universally agreed definition of what's considered as a "
medallion" in
Roman numismatics, but it doesn't necessarily imply large .. just any coin-like object that wasn't really a coin - something struck for a special occasion, likely without any
standard denominational value.
Here's what
Toynbee (author of a book on
Roman medallions) has to say:
http://numismatics.org/digitallibrary/ark:/53695/nnan8359There are a number of smaller pieces that arn't really coins (e.g. festival of
isis, or O C-S C/star pieces), but nothing else
comes to mind with
Constantinopolis on it.
In general there are for sure a few things in
RIC that don't really exist, or are misdescribed. I'd be a
bit suspicious of anything where
RIC could only cite something like
Cohen or
Voetter, not an actual known specimen the authors saw for themselves.
Not related to medallions, but here's an example.
RIC VII Rome 341 cites only a specimen in the
ANS, but the
ANS coin, below, is in fact from
Aquileia !
http://numismatics.org/ocre/id/ric.6.rom.341Incidentally,
RIC 342-343 likely also don't exist - they are probably misattributed specimens of the later
RIC VII Rome 52-53, from which they could only be distinguished based on
bust style.
The
ANS OCRE "online
RIC" database makes the same mistake and illustrates specimens of
RIC VII Rome 52-53 in place of
RIC 342-343.
http://numismatics.org/ocre/id/ric.6.rom.342http://numismatics.org/ocre/id/ric.6.rom.343Ben