Actually the
Paris example reported by
Cohen 867 has
COS II in
exergue, like yours. It is illustrated by
Strack pl.
VIII, 802; from different dies than yours.
Strack 802 and
Cohen 867 both misdescribe this piece, by not mentioning that the
COS II is in
exergue.
Strack 802 lists a second example of this coin, in Bologna. One wonders whether it is of the same variety as yours and the
Paris coin, or the one with
COS II in the circular
legend.
I have a specimen from the same dies as the Ritter coin you show, with
COS II in circular
legend.
Another conundrum:
BMC p. 180 copies Cohen's description as no. †, meaning not in BM
collection, but in the footnote they assert that the BM now has such a coin. But there was no such coin among the eight that came up when I searched their online
collection for Antoninus
sestertius Securitas. It looks as though that notation "Now in B.M." may have been misplaced in the
BMC footnote, and was meant to apply to some other coin.