RIC only lists this type from Trier; but they were also struck at London, Ticinum and Aquileia. Based on style, this one is from Ticinum. Pierre Bastien published two articles about these coins in the 70's.
Bastien, Pierre. “Une emission de folles sans marque a Ticinum en 312.” Schweizer Münzblätter 20 (1970) : 114- 115.
________. “Folles sans marque emis par Constantin en Italie.” Schweizer Münzblätter 24 (1974) : 5- 8.
Lech has this type here--
https://www.notinric.lechstepniewski.info/6tic-115_unm1.htmlConstantine I
A.D. 312-313
21mm 4.4g
CONSTANTINVS P F AVG; laureate and cuirassed bust right
MARTI CONSERVATORI; helmeted & cuirassed bust of Mars right
RIC VI Ticinum ---