Constantine II. AE3 (20.27mm). London, 324-325 AD. 

CONSTANTINVS IVN NOB C, laureate, draped, cuirassed bust right
seen from the back.
PROVIDEN-TIAE CAESS, campgate, 2 turrets, 6 layers, star 
above, no doors, dot in lower doorway and dot above doorway. 

Mintmark PLON in exergue
RIC VII London 296 var (dots); cf Sear 3946

Another of these with the dots in and above the doorway is
in the beastcoins collection.

Used with permission of TimeLine Originals (www.time-lines.co.uk), November, 2009