Antoninus Pius 138-161 AD. as. 26 mm. 9.97 grams. 

Rev: MVNIFICENTIA AVG celebrating the 900th anniversary of Rome. 
 (His munificience in giving the games.)  COS IIII in ex. 

Struck 148-9, 900 years after the founding of Rome in 753 BC.  

Sear II 4307. RIC 861 "scarce" Foss 52 (event of 147 AD).  

From Warren Esty's website, http://augustusmath.hypermart.net/coinlist.html,
[reduced to $45] January, 2006.