South Africa 1937 Empire 1½d Air Mail Scheme Second Northbound

1937 EMPIRE 1½d AIR MAIL SCHEME: Second Northbound flight of the "All Up" mail Durban to England. Cover franked Coronation 1½d clearly tied by Durban canceller 4 VII 37. Promtional cachet detailing the new postage charge applied in red. See scan. Forwarded upon arrival in UK, no backstamps. Attractive cover.