Air Post stamps. 1930, Zeppelin issue, complete proof pane of 25 ''CORREO AEREO. R.S. 6-V-1930'' overprints in brown, printed on thin paper, representing all existing plate varieties, several folds did not detract, VF and extremely rare piece, expertized by C. Beltran and Matthew, Est. $1,000-$1,500 (Image)

Air Post stamps. 1930, Zeppelin issue, surcharge or overprints on Aviation School stamps in various colors, set of six (without No.C13 and C17), nice quality, full OG, NH, mainly VF, C.v. $450 as hinged, Est. $200-$300 (Image)

Air Post stamps. 1930, Zeppelin issue, double blue overprint on 10c vermilion and black, full OG, previously hinged, F/VF, C.v. $175, Est. $100-$150 (Image)

Air Post stamps. 1930, Zeppelin issue, double red overprint on 25c dark blue and black, full OG, previously hinged, fine and very scarce, only 25 stamps have double red overprint on this denomination, guarantee hs on reverse, C.v. $550, Est. $250-$400 (Image)

Air Post stamps. 1930, Zeppelin issue, inverted brown overprint on Aviation School stamp of 50c orange and black, full OG, LH, VF, Champion guarantee hs, C.v. $225, Est. $150-$200 (Image)

Air Post stamps. 1930, Zeppelin issue, surcharge 5c/10c and overprints with bronze powder on 10c-1b, complete set of five, nicely centered, full OG or unused, no gum (15c), VF and scarce, C.v. $1,120, Est. $500-$600 (Image)

Air Post stamps. 1930, Zeppelin issue, green with bronze powder surcharge 5c on Aviation School stamp of 10c vermilion and black, block of four, full OG, NH or LH (top stamps), VF and scarce multiple, only 300 were printed, bottom left stamp has tiny expert's pencil sign, C.v. $480 as hinged singles, Est. $300-$400 (Image)

Air Post stamps. 1930, Zeppelin issue, inverted blue with bronze powder overprint on Aviation School stamp of 10c vermilion and black, full OG, LH, VF and rare, only 50 stamps were produced, expert's hs on reverse, C.v. $200, Est. $150- $200 (Image)

Air Post stamps. 1930, Zeppelin issue, double violet with bronze powder overprint on 15c carmine and black, full OG, previously hinged, F/VF and rare, only a handful was produced, guarantee mark on reverse, this stamp is not listed in Scott, Est. $300-$400 (Image)

Air Post stamps. 1930, Zeppelin issue, inverted copper overprint on 25c dark blue and black, full OG, barely trace of hinge, VF and rare, only 50 stamps with inverted copper overprint were printed, Est. $150-$200 (Image)