Well, I thought I ought to look inside the cavity covers of my MK signature, which has LED markers down the side of the neck.
 
Under what I correctly assumed to be a battery cavity was no less than 4 batteries.  To my surprise, on removing the main control cavity there is another battery.  Can someone shed some light as to what all these are for?

Hi Allen
The multiple batteries in the seperate compartment power your leds...
the single battery powers your preamp...

Sorry for misspelling your Name alan