This is an EA117. BUT, I've looked into it, and it I'm sure it's a licenced copy sold by Habitat in the late 80's / early 90s. All the design details you would expect to find on an authentic chair are present, but there's no logo or signature. Habitat sold these for a very short period before there was a falling out with Herman Miller.
Anyway, there are a couple of flaws: The leather upholstery has a sag in the seat. The gas cylinder slowly deflates - you sit on it and find yourself going down. When it's down, it's a comfortable lounge chair, but it's too low for my desk. The leather has the number of scrapes that you would expect for its age. The aluminium has lost its polish.
Looking for £90, collected, from UB2 area.