Where is the reverse switch on my J reg Escort XR3I convertible?

I went to the Ford Garage the other day and purchased a switch for my J reg Escort Convertible, I have looked in a Haynes manual which tells me the switch is screwed into back of the gearbox but I cant find anything that remotlely looks like the one I was sold. The one I have is a long metal thing with some sore of bearing in the end and has a plastic "Toblerone" type connector. Was I sold the wrong thing, or am I just stupid???