Edward III Groat ?

I cannot speak for the Spink # as I don't have the book, but I'm inclined to agree with your attribution. First I wasn't sure because the legend in my book did not match one-for-one with what I see on your coin, but it says there that "letters are often missed out or words misspelled in the legends and LONDON is sometimes spelled LONDOM"
What goes for your dating it as 1351 - 52 is Lombardic "M", closed "C" and E", and, most importantly, "R" with wedge-shaped tail. All later issues appear to have "R"s with normal tail.