Allectus. AE Antoninianus. London mint. 

IMP C ALLECTVS PF AVG, radiate, cuirassed bust right.
SALVS AVG, Salus standing right, feeding serpent in arms.

S-A across fields. 
Mintmark ML. 

RIC V-2, 42; Sear 13845.
Rare.

Sold by Aurea Numismatika - Auction 53, Lot 2873, Dec. 2013.