From my research and understanding 1905 was the date the 404 was introduced by Jeffery and since Rigby was the sole importer of commercial Mauser actions many makers chose to "mutilate military Mausers" ( as Rigby called it ) rather than pay the price Rigby was demanding for properly demintioned actions.
The Jeffery serial number, on both the action and barrel, places this rifle as being made in 1905.

it is certainly a slim and handy rifle that has obvioulsy been well used but remains solid and serviceable.

This then would be the rifle that set the bench mark for Rigby when they decided to build their 416 and for H&H when they offered their magnum 375.