Textbook pre war M31 canteen marked FWBN 37

Textbook pre war produced M31 canteen in very good condition. The canteen is in excellent condition, only the felt cover features some m other damages. The canteen is nicely marked FWBN 37 which indicates production by F.W. Brockelmann Aluminiumwerk GmbH KG, Neheim/Ruhr in 1937, the cup is dated 36 which is most likely a factory mismatch which is remarkably pretty often encountered by this manufacturer! Nice pre war example in excellent condition!