They were made in different factories, some in canada, others in germany, so they are ever so slightly different to look at if using a microscope, most peeps won't even notice, I have a canadian one on mine, whereas a german manufactured one came off.
They will interchange perfectly, the main difference is inside the tank, the oe ones with plastic swirl pots, had the swirl pots made by mercedes supplier, hence there being a merc emblem on them, later ones made elsewhere.
They will defo 100% interchange ok, some, a few, had a 3/4" lower main inlet in the tank, so the breather pipe that goes onto the side of the main fill up funnel pipe that goes to tank will need chopping and extending by 3/4", otherwise the main fill pipe will try to twist as you attach it and get it screwed into the cap area, as the breather pipe is not straight but curls round slightly the main filler.
This affected mostly the canadian ones, but 5 mins with a bit of pipe soon cures that.
tabetha