Strack knew only one specimen, so certainly
rare.
His concern was to
catalogue the existing
types, and he made no attempt to categorize
rarity.
One has to bear in mind, though, that a huge number of
new coins have turned up since
Strack visited European museums and private
collections and perused sale catalogues around 1930.
Strack didn't visit many quite important
collections, for example
Glasgow,
Cambridge, Turin, Madrid, Stockholm, Belgrade,
ANS. Moreover, not many public
collections have made an effort to acquire every variant of every series of
ancient coins; what they have is somewhat haphazard, and large numbers of
rarities that they are missing remain in private
hands or on the market. So though your
dupondius seems to be the second recorded specimen according to
Strack, a thorough
search today might well turn up several or even 5-10 other examples. Plus, the
rarity of a particular variety has very little effect on the market value of an ancient coin, except in fields where there happen to be at least two well-off, specialized private collectors striving for completeness,
as is the case at the moment for
Roman coins of
Gordian III and of
Probus!
As to your Pius
dupondius, both I and Frans Diederik have a special fondness for the coins of Pius and would certainly be very happy to acquire it, but neither of us would pay a large premium for it, since we know that there are large numbers of other
rarities regularly coming up and
selling very reasonably, plus neither of us is rich!
