Actually, as I recall they are. The VFD is definitely the same. The MK2/a boards differed from the MK1 versions in being smt rather than trhough-hole, and having the rotary control, different psu circuit, etc. Functionally they're compatible as far as I can remember. I'd have to check my notes to be absolutely sure.

The VFD can be transplanted from a MK1 to a MK2 board just by unsoldering and resoldering. Fiddly but not difficult.

pca