Coding on back of wiper switch?

Have a dash wiper switch for my 71 fasty which I think could be the same as some of the kombi switches.

Anyway..........the 2 water outlets from the switch are coded "B" and "D". Can anyone tell me what these mean and can the water hoses go on anyway?

Thanks.

at a guess ide say b is for bottle and d could be for dash ,but thats a guess