RAF officer's documents and maps brief case

RAF officer's / navigator's documents, maps, brief case.
This faded light grey canvas & black leather trim case has the Air Ministry & Kings Crown emblem on the flap front (albeit feint, see photo's) and the War Department arrow with a Ref. No.6B/469, stamped on the inside with the Officer's name.
It has a metal lock on the flap (key missing) which opens to reveal inside three sectional compartments.
Bag size, 18 x 14".
The bag is in a good condition with some usage wear. 
It has two leather retaining straps (one damaged) which when used adds to the case security.