I bought this coin yesterday...it's a bit scarcer but not really special. What I liked is that it is ex-James Pickering, who some of you might know from online discussions. He had some websites including a nice London mint page, but they seem to be down.
I have it on my London page which I recently updated with references from Cloke and Toone "London Mint" and also added some of the specifics from the book about the coins, like this --
May-Nov 307 first reduction, struck at 42 coins per Roman pound with a Pearl Ring Diameter (outer beaded circle) of 24mm and avg. weight of 7.7g
Constantine I
A.D. 307
29mm 9.3g
FL VAL CONSTANTINVS NOB C; laureate, draped and cuirassed bust right.
GENIO POP ROM; Genius standing left, tower on head, loins draped, r. holding patera, l. cornucopiae.
In ex. PLN
RIC VI London 89b; LMCC 5.01.009
