ETI, the French mid-market, 250 to 4,999 people
The band an assembler model fits best. Large enough to have real transformation budget and real legacy systems, small enough that one conversation with the top of the house settles it. Frequently family controlled, frequently industrial, and almost never approached by anyone who is not already known to them.
Who signs: the directeur general, the deputy or executive committee member who owns growth, the transformation or systems director, and at family groups the owning shareholder.