I believe it was 1905 when the British outlawed the 450 bore in India and the Sudan.
The 475 No2 is NOT just a necked up 450 No2. The diameter if the rim is bigger and the base of the case is larger.
Also the 475 No2 uses different diameter bullets than the 475 No2 Jeffery. [475 No2 480 gr. .483 dia vs 475 No2 Jeffery 500gr. .488 dia. if I remember the diameters correctly.]