AE 3, 2.95 g, London mint, CE 321-322
RIC 224 (R3)
O: CONSTANTINVS AVG
R: BEATA TRAN-QVILLITAS/VOT/IS/XX/ PLON
Ex: Dr. Tom Buggey (TN)
cf. his website: http://tjbuggey.ancients.info/romeae2.html
The above photo is Dr. Buggey's.
He had the weight listed as 2.76 g, but weighing this on different scales revealed a weight as noted above. What the photo does not reveal is the pleasant green patina on the coin.