Got to be later. All my bars have the rake on them, stamped, unstamped, johnny chopper replica. Looking at the 82-83 mongoose catalog the stainless bars don't seem to have the rake.
Are they also 23" wide Rowan?
Check out "Blogging a dead horse" on the net, there might be some info on there.
Next time I see my neighbour I'll check out his Malvern Star catalogue collection for some clues but it looks pretty complete.