726th V -Mail ( Victory Mail)

From Wikipedia 
V-mail stands for Victory Mail. It was based on the similar British "Airgraph" system for delivering mail between those at home in the United States and troops serving abroad during World War II. V-mail correspondence worked by photographing large amounts of censored mail reduced to thumb-nail size onto reels of microfilm, which weighed much less than the original would have. The film reels were shipped by priority air freight (when possible) to the US, sent to prescribed destinations for enlarging at a receiving station near the recipient, and printed out on lightweight photo paper. These facsimiles of the letter-sheets were reproduced about one-quarter the original size and the miniature mail was delivered to the addressee.
V-mail used standardized stationary, 7 by 9 1/8 inches (17.8 cm by 23.2cm) with a glue flange on one side so that the letter could be folded and sealed in such a way as to become its own envelope. When used by overseas servicemen the letters were opened, censored and photographed. Only the film negatives were transported. After transport by air, reduced-sized versions of the letters were printed from the negatives for delivery to their final destinations. These 60%-reduced photocopies measured 4 1/4 by 5 3/16 inches (10.7cm x 13.2cm), and had a pre-formed crease 1 7/8 inches from the top. The crease insured that the address would be correctly centered behind an opening in a special envelope. The user would write the message in the prescribed space—ideally in black ink, since this photographed best (the Carter ink company marketed a special "V-Mail Ink")— fold the letter/envelope form, address it, affix postage and then the mail was on its way.
According to the National Postal Museum, "V-mail ensured that thousands of tons of shipping space could be reserved for war materials. The 37 mail bags required to carry 150,000 one-page letters could be replaced by a single mail sack. The weight of that same amount of mail was reduced dramatically from 2,575 pounds to a mere 45." This saved considerable weight and bulk in a time in which both were hard to manage in a theatre of the war. It also eliminated the threat of spies using microdots or invisible ink to send reports. Any microdot would not be photographed with enough resolution to be read.
Although the system of V-mail ensured that more pieces of mail were able to be shipped and delivered than a larger, bulkier mailing would have accomplished, many people found that they did not have enough room in the limited available space in order to write all that they had to say. To make things worse, the instructions at the top of each letter stated that "very small writing is not suitable".