During an extensive re-listing of my collection I came across this Mule Penny which is described here. Effectively the current Corpus of Series G Pennies from London are only recognised as starting with Gc Obverses but this coin is clearly a Gb Obverse (Annulet Stops not Saltires) matched to a Gf reverse.
Edward III 4th Coinage Pre-Treaty Period Series Gb / Gf Mule Penny, London Mint – Duncan Russell
BNS Research Blog 
Hi your introduction header has a typo mistake the obverse has annulet stops not pellet stops
Now corrected…