Air Post stamps
1930, Zeppelin issue, trial silver overprint "Correo Aereo. R. S. 6-V-30" on Aviation School 50c orange and black, full OG, LH, VF and scarce, only 25 stamps were produced, Beltran guarantee hs, B. Moorhouse certificate, Sanabria (1961) #27A, C.v. $350