I have been buying too many coins of late
Sure sign that the economy is on the mend ! Personally anyway.
I found this one a few weeks back. Not quite as 'buff' as I would like it to be but the better ones tend to be pricey (maybe next time)
Antoninus Pius Orichalcum Dupondius
Obv Radiate bust right ANTONINVS AVG PIVS P P TR P XVIII
Rv Britannia seated on rocks in attitude of dejection shield and vexillum in backround BRITANNIA COS IIII S C
Sear 4266 RIC 930
23-5mm 9.95 grams
Rome Mint


David Sear speculates that many of the copper As denomination were produced in Britain itself (based on the inferior quality) but does not make the same statement regarding the dupondius. Presumably none were produced of "inferior quality".
Which harkens back to a belief I have that orichalcum coinage required special equipment to produce.
The primary source of zinc was Britain. Why produce a copper as locally when with a "dash" of the local calamine added into the mix you might knock out the dupondius (double the value !).
Next I need to find a BRITANNIA As