WG (Royal Numismatic Society) identifies JT.
William Glibert, "Talismans," The Numismatic Chronicle and Journal of the Royal Numismatic Society 18 (1938): 274
On the left the astrological symbol of Jupiter. Between the inner circle and the edge is the Latin inscription, CONFIRMO O DEVS POTENTISSIMVS.
A publically accessible link can be found here: https://archive.org/details/in.gov.ignca.1246/page/n283/mode/2up
While the translation of this phrase seems to be publicly accepted as "strengthen me, o most powerful God", this is a unique way of expressing that idea. While confirmare is typically a transitive verb that has an active sense, here it is rendered as a middle intransitive verb (intransitive as the object is not explicit) or as a imperative with an object would be.