There are variations of the overriders - so potentially eight versions, but I have only seen around 6 in all my years playing with Mk2 Escorts..
You have the with or without bumper rubbers, big or small (ie late or early) , and fluted or non fluted.
The without bumper rubbers are for the rally packs as the L models probably did not have them.... so fairly rare
Early (pre 77ish) cars had a smaller (protruded less) type (dont quite look as nice as the later ones - but beauty is in the eye of the beholder of course)
Later ones came as a little more deeper and rounded and came in fluted and non fluted.... These later ones are the more common ones....
Most common problem is that the screws that hold the tabs that hold the overiders on the bar, rust and either you cannot get them off, or destroy the rubber trying to prise them off....
When I first got my first Escort in 1988, and Escorts were relatively common in normal wrecking yards, I spent a lot of time going through the yards to find a full good set of ones for my 79Ghi that only came with one when I got it... (They do make the car look nicer - especially a Ghia or highers spec car) in my opinion. Even in 1988 I spent a lot of time trying to find decent ones, and it has been years since I have seen a serviceable one.... Most cars I have got over the last 10 years have not even had one. (I had a pair sitting upside soaking the screws in penetrene for about 2 years, but even that did not free up the screws...)