Help with markings on a Justin I

[Paul B4]

Do you know know the meaning of the 2 stars on the reverse?
It looks like an officina mark below the M.  What is the mark and what does it mean?
13.25g, 28.6mm
BCV 83

[Paul B4]

Here's the coin.

[Obryzum]

Below the M is the officina mark  -- which is just a fancy way of writing 

Nobody really knows for certain what these mean.  Some have suggested that they designate different "workshops" within the mint. 

[SC]

They were likely issue marks - like the different letters and symbols found in the fields of late Roman (4th century) coins.  Not meant to be understood by the public but allowed mint and state accounting and control.

SC

[vercingetorix]

  is Greek numeral 1 and refers to the first officina (workshop) in the mint of Constantinope, which had five workshops, marked on coinage         
The stars are what numismatists call "privy marks" used by mint officials to distinguish between different series. W. Hahn has used these to date the coinage more precisely (Moneta Imperii Byzantini reference catalogue). On the coinage of Justin I and Justinian I we see most commonly a combination of stars and crosses on the reverse.