Translation of legend abbreviations:
A(VTOKPATΩP) K(AICAP) M(APKOC) A(VPHΛIOC) NOVEMPIANOC CEB(ACTOC)
Imperator Caesar Marcus Aurelius Numerianus Augustus
L Γ
year 3
EGYPT, Alexandria. Numerian
year 3, CE 284/5
potin tetradrachm, 20 mm, 7.25 gm
Obv: AKMANOVMEPIANOCCEB; laureate draped bust right
Rev: Nike flying right, holding wreath; ETOVC - Γ
Ref: Emmett 4022(3), R2; BMC 2469
CNG e324, 9 April 2014, lot 707
This coin came from a large lot of Alexandrian tetradrachms, most of which had been "treated" by a previous owner with what appeared to be women's makeup, mimcking a sandy patina. Fortunately the makeup was easily removed and hopefully no harm done. I soaked the makeup off all the coins, treated with Verdicare, and I inspect them regularly. The makeup does appear to have caused corrosion (verdigris) underneath but hopefully the rapid corrosion has been halted.
This is the problem I have with applied patinas-- what might they be doing to the fabric, out of sight? I routinely soak my newly acquired bronze coins in water, acetone, and alcohol (some or all, separately) and treat with Verdicare if there is any suspicion about the patina.