Unfortunately thereís really not too much information out there on these knives. I see you have already posted the knife for review on the Australian Blade Forums and they provided the following link of the single edged variant Australian Military Knives - Knuckle Knives I assume you have seen the double edged variant here Military Fighting Knives/Collection too.
I wish I could add to these two sources as it is a rare and desirable knife. Please, share with us if you receive any further sources as there are many fans of all things pointy on this forum. The blade looks pristine. Thank you for posting your knife.
I followed the link on the AWM site and also knew of the one on John's site that you mention.
I was lucky enough to be able to obtain the Randall model 2 knuckle that John sold some 10 years ago a little while back as well, and also recently picked up a very different theatre style knife that I am still trying to research.
I read on a site somewhere about copies of Gregory knives but have not managed to find out any more.