all of the mkI's i have are 24 hr display. i have one that has the dot in the upper left corner. i have not figured out why. in roger's early ads he states 12 or 24 hr display, but i haven't seen a 12 hr one. i have 12 mk I & II's and they are all 24 hr plus one i made up for a friend who had one of the originals also. i also had noticed the different way the monsanto digits are connected, but it never dawned on me that some are upside down. i just thought that was the way they had to be in order for the display to look right. i need to examine some i have been working on. maybe that is why the display is not right on those that i replaced the display.
egomon, that one you have in your photo is a very early one. the segment and digit driver transistors on the later ones are different. i have a very clean pcb with those transistors that i have been wanting to put a chip and display on and see if it will work. peter