I was going through my CNG wins and found this coin. I am thinking that it looks like Trier (RIC VI Trier 884); but Dr. Malcom Lyne thought London. I am wary of my own judgement in this circumstance and would like to crowdsource this.
Constantine I
circa A.D. 312
21x22mm 3.8g
CONSTANTINVS P F AVG; laureate and cuirassed bust right
MARTI CONSERVATORI; helmeted & cuirassed bust of Mars right
here's a Trier 884