These three-letter abbreviations identify English counties (pre-1974):
BDF Bedfordshire
BRK Berkshire
BKM Buckinghamshire
CAM Cambridgeshire
CHS Cheshire
CON Cornwall
CUL Cumberland
DBY Derbyshire
DEV Devon
DOR Dorset
DUR Durham
ESS Essex
GLS Gloucestershire
HAM Hampshire
HEF Herefordshire
HRT Hertfordshire
HUN Huntingdonshire
KEN Kent
LAN Lancashire
LEI Leicestershire
LIN Lincolnshire
LND London (city only)
MDX Middlesex
NFK Norfolk
NTH Northamptonshire
NBL Northumberland
NTT Nottinghamshire
OXF Oxfordshire
RUT Rutland
SAL Shropshire (Salop)
SOM Somerset
STS Staffordshire
SFK Suffolk
SRY Surrey
SSX Sussex
WAR Warwickshire
WES Westmorland
WIL Wiltshire
WOR Worcestershire
YKS Yorkshire
ERY Yorkshire-East Riding
NRY Yorkshire-North Riding
WRY Yorkshire-West Riding