Unfortunately it is a bit cryptic... I am going to talk to s&b about marking these things....
If you have the lowest tap as 46db and 19 taps total then it is a MK I. A few MK II's also have only 19 taps but most all have 23 taps
If it was bought in the last few months it is a MK III
All else is MK II
I can tell right away when i measure them here but I know that only works if you have test gear!
Post a description of what you have and it's history and I'll get to the bottom of it for you.