The
style looks OK to me, so I would accept the coin as official, apparently with a striking error of some sort cutting off the back of Liberalitas'
head.
My first thought was, maybe a
flip strike with the second strike transferring the
obv. legend to the
reverse, removing all traces of the original
legend LIBERAL AVG COS but curiously leaving the
rev. type unaltered. But the
legend break SEP -
SEV is definitely wider on the
obv. than on the
rev., so this is not two strikes from the same
obv. die. Plus the
obv. of a
flip strike should
still show remains of the
overstruck rev. type, but none are visible. We would have to postulate that the second strike with the
obv. die completely eradicated the original
Liberalitas type and
legend. Highly unlikely, so certainly not a
flip strike.
So I think Timka's explanation is probably correct: a
mint engraver erroneously
engraved an
obverse legend onto a
rev. die. This is the first time I can recall seeing such an error, but it is perfectly possible that parallel cases have been published, and I am just unaware of them. One could easily read about such an error in a footnote or appendix, but consider it unofficial or just an unexplained oddity, so quickly forget it!
