Bidspirit auction | Liechtenstein - Air Post stamps

Liechtenstein - Air Post stamps - 1930, Airplane over Mountains and Vaduz Castle, 15rp-1fr, complete set of six, in addition black surcharge 60(rp) on 1fr lake, nice quality, four of seven stamps with sheet margins, full OG, NH, VF, E. Diena certificate for the set, C.v. $648, SBK #F1-6, F16, C.v. CHF970, Sc. #C1-6