A nice find! A
rarity that I was not aware of.
Strack 164 actually knew three specimens of this
denarius, two in
Berlin (one illustrated on
his pl. II), and one in
Sofia.
Checking
CoinArchives, I find that a nice specimen was offered by Gitbud & Naumann in 2014, but I obviously overlooked it, since I don't remember bidding for it, and it sold quite cheaply at 55 euros plus fees! See image below.
The same
type also occurs on
aurei, as you mention, and on bronze coins, where its
legend was
FELICITAS AVG S C,
COS IIII having been moved to the
obv. legend. I note that there are a number of minor varieties of the
type: Felicitas may place her
weight on either her right or her left
leg; she may hold her
caduceus either towards the top with bent l.
arm, or toward the middle with extended l.
arm; and the
caduceus may be either winged or without wings. Compare the
aureus below, where her
weight is on her left
leg (r.
leg bent), she holds the middle of the
caduceus with extended l. forearm, and the
caduceus lacks wings.
On the three illustrated
denarii (yours, Berlin's, G & N's), Felicitas places her
weight on her r.
leg, her
caduceus lacks wings, and she holds the
caduceus higher with bent l.
arm, though this detail seems a little obscure on your specimen.