Johnson,
Welcome to the forum and thanks for posting those photos!

Yes, as we have discussed earlier, your rifle is the real deal true blue Manchester Whitworh Express for sure.
It has all the right stampings to verify it's originality.
Both 7mm Rem mag and 300 Win mag are listed for Whitworth Express rifles in a 1976 Guns Illistrated which I have here.
Your rifle proves that the 300 was definately produced so I just need someone to confirm the 7mm Rem.
The stamped numbers on the right side cannot be accurately relied upon as to the date of assembly IMO.
They do provide an approximate dating however.

Did I mention that I'd be happy to swap stocks with you!

That leftside buttstock grain is sweeeeet!