Tiberius as Caesar (under Augustus) Lugdunum/ 8-11 AD. Joe Geranio.

As we get into the late coinage of Augustus from 8-11 AD we see a big bronze from Lugdunum (I love this mint by the way).  TIBERIUS. As Caesar, 4-14 AD. Æ Sestertius (25.45 gm, 1h). Lugdunum (Lyons) mint. Struck 8-10 AD. TI CAESAR AVGVSTI F IMPERATOR V, bare head left / ROM ET AVG in exergue, the Great Altar of Lugdunum: altar enclosure; panels decorated with corona civica flanked by figures holding laurel branches; decoration along roofline; altar flanked by columns surmounted by statues of Victory standing vis-à-vis, each holding palm and wreath. RIC I 240 (Augustus); BMCRE 572; Cohen 28. Tiberius as Caesar 4-14 AD.  Translation on obv:  Tiberius Caesar Augusti Filius Imperator Quintus.
Tiberius Caesar, son of Augustus, supreme commander (Imperator) for the fifth time.  Translation on reverse:  Rome and the emperor (Augustus).  Image on reverse-  Altar of the three Gauls in Lugdunum, flanked by Victory holding wreath on column on each side, front decorated with corona civica flanked by nude male on each side.  The “M” counterstamp I’ve seen on both obvers and reverse of this issue. An “M” punch C/M could have been applied under:
• Claudius
• Nero
• Or even during the civil war period of AD 68–69.  Don’t forget Tiberius was officially adopted in 4 AD.  

For Tiberian sestertii (including RIC I 240), distinguishing Lugdunum issues from later Rome mint issues (after AD 22/23 under Tiberius) comes down to fabric, portrait style, and lettering.
Joe Geranio- Julio Claudian Iconographic Association.

Thanks for posting this interesting coin with C/M. Is there any authoritative sources or speculation on what the “M” signifies historically. The C/M ‘VAR’ stood for Varus of Teutoberg Forest fame, and I collect the Judean issues for the Legion X Fretensis, but I can't recall reference to ‘M’. The Museum of Roman countermarks (  http://www.romancoins.info/CMK-Lugdunum-Aug.html  ) doesn't list it either. I not sure why, or how, this would have been applied by later emperors. 

For Moneta?  

Bakers old countermarks and stamps have been very helpful over the years.  cant remember source off top of my head for M. His guess was Moneta.