Don't know all of them. 
The first letter is the target market.
UY
U = USA Model
Y = BNC Connectors
BX
B = British Model
X = No Terminal Board supplied as standard.
EX
E = Europe Model
X = No Terminal Board supplied as standard.
EK
E = Europe
K = Charcoal Gray Finish
ES
E = Europe
S = Silver Finish
.
The first letter is the target market.
UY
U = USA Model
Y = BNC Connectors
BX
B = British Model
X = No Terminal Board supplied as standard.
EX
E = Europe Model
X = No Terminal Board supplied as standard.
EK
E = Europe
K = Charcoal Gray Finish
ES
E = Europe
S = Silver Finish
.
