I just saw this listing on eBay. I guess it is all a matter of perspective, and I can see how you might see flames if you are not familiar with the altar design...it's like a Rorschach test. He also had it listed as being from London.
ROMAN COIN OF CONSTANTINE II 316-340AD - VOTIS XX FLAMES ON ALTAR #260
“LONDON MINTVERY NICE CONDITIONâ€
I have added an artistic rendering of altar with flames for comparison.
