I have ventured into the late 3rd century, and this is one of my most interesting finds up until now:
TACITUS AE22mm 3.55g billon Double-Aureliani (F, worn)
AV: IMP C M CL TACITVS AVG; radiate, cuirassed and draped with paludamentum bust r.
REV: CLEMENTIA TEMP; Mars in military dress stg. (or walking) l., holding olive branch in r. hand, spear and shield which rests on ground in l. hand. Star in left field.
EXE: I A
REF: RIC V-1 214, BNC 1846, Online RIC Temp no. 4113, jan. - jun. 276AD. Quite scarce, 10specimens recorded by S. Estiot.
This type was minted at the scarce mint of Tripolis and is considered to be an unusual and rare denomination called the Double-Aureliani (or Double-Antoniniani, for those who still keep the denomination name from before Aurelian's reform of 274AD.) because it contains twice the amount of silver in the alloy than the regular XXI or KA Antoniniani. This specimen was EDX tested and came at 3.06% silver in the core while 19.6% silver at the surface.
Specimen previously published in Numismatic Chronicle, 1993: "The Alloy of the XI Coins of Tacitus." entry 92.3.
PROVENANCE: 2014 ex. Warren Esty.