I also have one of those! A Z5540 small Wembley.
Your lantern therefore seems to be a hybrid of the 2 types.Perfect conclusion there and great to see some more photos of your lantern too.
My apologies to Davy for purloining his image btw (it is for a good cause though).
Actually, it is interesting to discover that this one is a little different - like you say, it is a bit of a hybrid. I wonder how long it was in production for?
With regards to restoration, as I am now thinking it would have had a wire ring for the bowl after all, I ought to be able to fashion one myself. To complete the job, I do have an acorn bowl tucked away somewhere too. The reflector will be a little more tricky to work out, although I do have something which could be adapted if I'm really pushed.
Good old GEC - always full of surprises eh?