check acsearch...they have several dozen examples-- some recent, some further back.
Your coin does not have a star in the mintmark, but a dot in the exergue. The author of RIC, Patrick Bruun, mentions this coin in the footnotes....
It Rome mint-- SM leaf RB
I've got an example of the earliest Licinius campgate with SMHT mintmark [ATTACH]
I also agree that it is unofficial. I have had some good style unofficial coins copying Ticinum, like the two below. [ATTACH] [ATTACH]
This is RIC VII Cyzicus 55 with annulets on the diadem. [ATTACH]
These orbs are usually believed to be celestial spheres rather than the earth...of course there is always debate. see 'Symbolism of the Sphere'...
[ATTACH] Constantius I A.D. 294-5 Ӕ Antoninianus 23x24mm 3.3gm CONSTANTIVS NOB C; Radiate, draped and cuirassed bust right. COMES AVGG; Minerva...
the Constantine is 22mm and the Gallienus is 21mm
because the countermark assigns it a value.
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