This coin has SMNAT as the mintmark instead of the correct SMANT. It is actually an engraver's error, rather than an unrecorded mintmark and it is the second example that I have seen.
Licinius I
A.D. 317- 320
18mm 2.4gm
IMP LICI-NIVS AVG, laureate, draped, sceptre in left hand, mappa in right hand.
IOVI CONS-ERVATORI, Jupiter standing l., chlamys across l. shoulder, leaning on eagle tipped-sceptre and holding Victory on globe in r. hand; eagle with wreath to l. on ground; to left, captive.
in exergue SMNAT
cf. RIC VII Antioch 27