Vintage ink signature, “Cordialmente saluti, Guglielmo Marconi, 23 Maggio 1912, Lisbon,” on a light green 5.5 x 3.5 card. In fine condition, with scattered soiling. On this day, Marconi gave a conference at the Lisbon Geographical Society to promote his system in order to win a contract for the supply and assembly of radiotelegraphy stations in Portugal. RR Auction COA.
