Issued on 25 August 1952, this striking triangular airmail stamp celebrates Giornata Filatelica (Philatelic Day) between San Marino and Riccione. The design features a vivid magenta floral bouquet set within a blue triangular frame—an iconic mid-century layout beloved by thematic collectors. Printed by the I.P.S. – Officina Carte-Valori, Rome, the stamp exemplifies San Marino’s elegant post-war commemorative style. Highly valued for its distinctive shape and clean typography, it remains a classic for airmail and event-thematic collections.