The cover of the month of May shows a stamp from 1952. It is part of the series – Paintings from the Princely Picture Gallery, Vaduz. A total of 21 stamps were issued for this series from 1949 to 1954. They were designed by Anton Frommelt (1895-1975) and produced in halftone gravure by Courvoisier. This particular stamp features a painting by Andrea del Sarto – a painter of the Italian Renaissance (1486-1530) – depicting a very feminine St. John.
As can be easily seen, the stamp is retouched on the cheek and on the back. This plate error could be assigned to the 9th stamp on the 1st sheet. In the present case, it is a marginal piece. For comparison, a stamp without plate error.