Escort Mk2 odometres only have 5 digits in them so when they get to 100,000km they will then start again from 0km. I would suggest that the + indicates that they do not know if it has been clocked or how many times...
These days you are looking more for condition that km as the km are not that important anymore unless it is low km...
I have a fe Escorts that are definately under 80,000 , but it is their condition that is important these days.