Bidspirit auction | Worldwide Air Post Stamps and

Worldwide Air Post Stamps and Postal History - Vatican City - 1951, Franciscus Gratianus, imperforate plate proof of 500L in deep blue (issued color), horizontal pair printed on pink paper, a small part of adjoining stamp at the top left, light ironed fold on the left stamp, no gum as produced, NH, VF and very rare, Est. $600-$700, Scott #C21