Anyone know if this is Norton?

Doesn't look like any part of a lightweight frame that I've ever seen Kieren. 

Looks a bit like what I think has been termed a sissy bar fitted to the rear of frame for a passenger to grab on to. 

Kieran, this diagram was taken from an early Norton Jubilee manual. It has the "central" ie concealed oiltank, so I guess it is for what would be described as the Deluxe ie with additional body styling panels, omitted from the later "naked" lightweight range.

There is nothing vaguely like the part you have shown.