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   Tiberius or Tiberius Gemellus, Æ20, (7.02g) 37 AD, Kingdom of the
   Bosporus, Diademed head of the King right, BAP monogram behind, IB
   date before. / TIBEPIOY KAISAPOS Laureate head right. RPC 1900 (as
   Tiberius, 7 examples known to RPC). 

   Coins of Tiberius and Caligula (RPC 1901, 8 examples known to RPC)
were both struck with young portraits, about which RPC notes, The    
pieces with the portraits of Tiberius and Caligula were probably 
made at the end of the reign; the Tiberian pieces are so similar 
to the Caligulan ones that it seems very likely that both were 
made withim a short space of time".

The IB on the obverse is denominational.