THE King's head will replace the more usual Queen's head on a special set of commemorative stamps to be sold in Hong Kong from next Tuesday. Perhaps the first stamps in history for which the legend Return to Sender, Address Unknown on the envelope would be likely to increase the value several-fold, the set features the face of Elvis Presley singing into a radio microphone. The 29 US cent stamps were launched by the US Postal Services on January 8, on what would have been Presley's 58th birthday. They generated so much interest that the US Post Office organised a ballot in which more than a million Americans voted on whether the stamp should show the slender Elvis or the more mature Las Vegas singer. Youth won by a mile. Long queues are expected at the Philatelic Counter of the General Post Office in Hong Kong when the collectors' sets go on sale on October 26.