Swallow Canopy
Chevvron
You are correct. There were 2 sorts of Swallow canopies = the older ones were a small perspex bubble mounted on a frame that more ply on it than the photo of 651 and the latter ones had the large type perspex without the ply sides. The canopy bubble on 651 is modified from another.
All the Air Cadet Swallows had the old style canopy. I have advertised on the internet for one with no success.