Bidspirit auction | Worldwide Air Post Stamps and

Worldwide Air Post Stamps and Postal History - Bolivia - 1930, Airplane over Bullock Cart (instead of River Boat), set of five die proofs of 15c in carmine, purple, green (cut down and mounted on card), red and brown, printed in thickened paper, no gum as issued, VF and rare, Est. $500-$600 , Sc. #C28