if I recall correctly the number 1 enfield's bolt face is larger than the number 4's which mimics the same contours as the bolt body. also the decockers are rounded on number 1s. unless they also tried updating the sights on the experimental number 1s they would have barrel mounted rear sights instead of reciever mounted like the one in the picture. the magazine is also consistent with a number 4 rather than number 1. the front sight post, forward stock band... all are parts consistent with a cut down number 4, I could see little use in the australian military experimenting with converting a number 1 to a number 4 when the time and money needed could have just been better spent adopting a modified number 4 instead.
all guns lost in a tragic smelting accident.
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