The National Telegraphic Review and Operators Guide in April 1857 documented the use of the number 73 in Morse code to express `` love and kisses '' ( later reduced to the more formal `` best regards '' ) .
In April 1857 , the National Telegraphic Review and Operators Guide wrote about the use of the number 73 in Morse code to mean `` love and kisses '' ( later changed to `` best regards '' ) .