Check out Ian Skennerton's The Lee Enfield Story, page 434. There is an "Experimental No. 1 Shortened & Lightened Rifle." Except for the disk, it looks just like the one in the image.
A few were made in England but a batch of 100 were made in Australia for army trials in 1944. Serial numbers are preceded by "XP" and were numbered from 1 to 100.
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