They are likely the same as used in modern OS maps - https://www.ordnancesurvey.co.uk/resources/maps-and-geographic-resources/map-abbreviations.html https://www

They are likely the same as used in modern OS maps - https://www.ordnancesurvey.co.uk/resources/maps-and-geographic-resources/map-abbreviations.html https://www.ordnancesurvey.co.uk/resources/maps-and-geograph...