While the origin of '73' has always been somewhat shrouded in mystery, the April 1935 issue of QST had a short article on the origin of 73. The article was actually a summation of a December 1934 discussion that appeared in a bulletin from the Navy Department Office of the Chief of Naval Operations. The Navy stated: "It appears from a research of telegraph histories that in 1859 the telegraph people held a convention, and one of its features was a discussion as to the saving of 'line time'. A committee was appointed to devise a code to reduce standard expressions to symbols or figures. This committee worked out a figure code, from figure 1 to 92. Most of these figure symbols became obsolescent, but a few remain to this date...the symbol most often used now is 73, which means 'my compliments' [or as commonly understood today, "best regards"]. The other figures in between the forgoing have fallen into almost complete disuse."
According to the American Radio Relay League (ARRL), Huelbe Garcia, PU3HAG, wrote about the character Dr Sheldon Cooper on the CBS situation comedy The Big Bang Theory. Evidently Sheldon, played by actor Jim Parsons, has worn a shirt on the show with the number “73” emblazoned across the chest, leading some to wonder if Sheldon is a ham radio operator. Supposedly, Sheldon remarked that “73 is the best number. Why? "73 is the 21st prime number. Its mirror (37) is the 12th, and its mirror (21) is the product of multiplying, hold on to your hats, 7 and 3. In binary, 73 is a palindrome, 1,0,0,1,0,0,1 which backwards is 1,0,0,1,0,0,1.”
