Canary Islands. 1937, Issue for use on Lufthansa Air Mail Service, red surcharge 50c on Spain definitive stamp of 1c blue green, top sheet margin vertical imperforated strip of three, top stamp with triple surcharge, middle one - double and bottom one - normal, full OG, NH, VF, only 50 such strips were produced and only a few survived intact, ex-Florence, Sanabria #10, b, d, Est. $150-$200 (Image)