Hi Ben,
nice to see you back on the forum after quite a long time of absence... 
Your thoughts sound plausible. The medicus "desing" on several references of that time with the large center second feature
seems to have been a great offer to various groups of users like doctors, nurses, even military staff I guess...
I would like to find a perfect example of a square cased Medicus - a design to die for. 
kind regards
Erich