The images lack contrast in critical places making certain details difficult to see. But the main features are clear enough for us to get close.
Your identification of the coin is essentially correct but without specifying the name of the mint it is ambiguous. Coins in RIC VII are arranged by mint, and the numbering starts over for each mint. So your coin is #214 for the mint at Siscia, during the period 328-329 A.D. RIC VII Siscia 214 is a Providentiae Campgate for Constantine I. The officina (workshop) mark appears ahead of the rest of the mark lettering, but in this case it is mostly off the flan. The residual mark SEEMS to suggest the letter is a Beta (for officina 2) but the image is not clear enough for me to be sure.
There is one thing about this coin that gives me pause, and that has to do with the configuration of the "headband" that the emperor is wearing. The two varieties for this coin type and its mate (#215) are a laurel wreath and a rosette diadem. What I can make out does not look like either. The attribution to #214 is based mainly on the obverse inscription, CONSTAN - TINVS AVG, accompanied by a laureal wreath. But in the image of your coin the inscription is fine, but it looks like he is wearing a square-cell diadem. If so, that would not correspond to anything listed. I am sure it is the wreath, but I would like to see a brighter and sharper image to be certain.
As others have pointed out, I don't think your coin is being harmed much by the jewelry mount, except for its exposure to wear and tear. If it is a normal variety, then you may as well leave it as a necklace, since it has little financial value ($10-20) and less utility in a collection. However, it is still in a decent state of preservation and should make a fine conversation piece as jewelry.
I doubt that it is a diadem on the obverse, but if it should happen to be so, then that would change everything.
Posted 05/11/2016 08:32 am
Looks safe to me from here!
to CCF!
