5c green postal stationery envelope (H&G B12) with added 1935 5c red brown and 20c violet (SG 298 & 300) tied by undated CORREOS DE BOLIVIA APOLO cancellation addressed to LA PAZ with type written 'Primer vuelo directo Apolo - La Paz' and LLOYD AEREO BOLIVIANO OFICINA LA PAZ arrival mark on front. This was the return flight by the German pilot 'Hermann Schroth' in the trimotor plane 'Huanuni'. A very rare flight. (Photocopy of page from the Carlos Royuela airmail Exhibit accompanies illustrating two similar covers, Unlisted by Muller).