Remember last week I had mentioned my C31 find. Well I thought I would give each of the four covers in that lot its own write up.
The first is rather ordinary EXCEPT for the fact that it's a double rate air mail. I've collected AMSDs for more than a decade, and double rates are hardly the norm. This was mailed September 20, 1940, from Fargo, ND, to Cleveland, OH, arriving there the next day, as documented by the receiving cancel on the reverse. SD entitles the envelope to be hand-delivered the same day, rather than waiting for the next scheduled delivery.
The air mail rate was 6c per half ounce, from July 1, 1934 until March 26, 1944. The special delivery rate was in effect for roughly the same period, July 1, 1928 through November 1. 1944.