Not seen anythinmg like it, but looking at the shape of the axle casing my money is on a standard Rover diff with a home made (from an old saucepan?) replacement pan welded on. You'll have to take it out to see what it is.
Just had a thought.. It could be off a later/newer type with fancy electickery stuff. It came from a bloke who works with MOD landies in a big box of stuff, just thought it would do any v8 (doh)