Matt wrote:

MK even have two incompatible busbar systems - old and new.

Three, actually:

(i) the original type with U-slotted fingers for Siemens MCBs;

(ii) single finger type when they changed to Merlin Gerin components c.
1992 - this type had a wider finger for the incomer connection and
finger bent over at 90 deg. from the bar;

(iii) the current K type, flat with all fingers the same and generally a
bit thinner and cheaper-feeling.

--
Andy