It could have something to do with its load capacity. I know the MK1 load capacity was measured in hundredweight (CWT). There were 6cwt (300kg) and 8cwt (400kg) vans. Difference between the two was that the 8cwt had a extra leaf in the rear springs than the 6cwt to allow for the extra load.
I've seen a few MK2 vans with the 'Ford Escort 40' badge and hoping someone can explain what the badge means.