Well, congratulations! Can't wait to see pics of that beauty.

Is there a space in the receiver on the left-hand side for a rotating safety lever like you'd see on a MkIII SMLE? Or is the left side smooth like a cavalry carbine? If the former, your rifle was probably fitted with the charger bridge as an optional extra by customer request.

Later commercial Lee Enfields from BSA were made on the SMLE pattern and had the rotating safety lever on the receiver just like their military MkIII counterparts.

The 21" barrel is unusual, though this could have been specified by the customer as well.

Does the knox resemble an SMLE or a Long Lee?

Pictures will tell us a lot.

Again, congrats!