The highly skilled Shoe and Bootmakers of Northampton use different methods to determine the various width fittings of their shoes, which can be confusing. The following is a short breakdown of the Letters/Numbers used for 'Normal' and 'Wide' width fittings.
John Lobb use 'E' for 'Normal Width fitting and 'EE' for Wide.
Crockett & Jones use 'E' for Normal Width Fitting and 'F' for Wide.
Tricker's use Number '5' for Mens Normal Width Fitting and '6' for Wide.
Barker, Charles Tyrwhitt, Cheaney and Church's use 'F' for Normal Width Fitting and 'G' for Wide. Barkers have a unique known as 'FX' which falls between a normal 'F' and a wide fitting 'G' and as such is very popular.