Regardless of all the why's and wherefores this combination is clearly incorrect as the No7 was issued with a No5 scabbard. The only exception to this general rule, as I understand it, was that when the L1A1 bayonet was issued with the new-issue L1A1 rifles, units were issued with the bayonets only and the No9's (and the Energa launchers incidentally.....) were returned to Ordnance scabbard-less for disposal. Scabbards being taken on for use with the L1A1 bayonets. The same happened on a smaller scale with Stens and the No7's when the L2 came on stream with the No5 bayonet.
Thinking out aloud, I think someones taken the No5 scabbard off this bayonet (thread 1) and sold it on with a cut down old No1 bayonet scabbard. I mean, how difficult is it to cut a No1 scabbard down to length?