Molecular Mk 6ME - (AKA the 3ME - but basically the Mk 3)
Marketed as the 6ME, this was the new version of the Mk II but with all the inconsistencies of the Mk II having been removed.
Wire modifications were used on the MK2 processor to eliminate the stack counter and the new instructions, so it would run as a Mk 1
The 3ME was the same processor with a smaller backplane limiting the number of peripherals.
It seems that core memory was dropped at this time and static RAM chips were used instead. The battery backup (solely for the memory) was in the form of lead-acid batteries.