Tetricus I AE Antoninianus. Cologne mint, AD 270-274. 19 mm, 2.69 g.

IMP TETRICVS P F AVG, radiate and cuirassed bust right.
SALVS AVG, Salus standing left by altar, holding patera and anchor, feeding serpent rising from the altar. 

RIC 123.

Image courtesy of Moneta of moneta-coins.com. Altar with serpent described as a "small figure".
Note: Many sellers describe this reverse type but with SALVS AVGG as RIC 123 in error. Such coins are RIC 127.