Issued by Monaco in 1958, this commemorative stamp marks the centenary (1858–1958) of the proclamation of the Immaculate Conception doctrine by Pope Pius IX. The design features the Marian statue associated with devotion to the Immaculate Conception alongside portraits of Pope Pius IX, emphasizing Catholic theological heritage. Printed in elegant dual-tone engraving, the issue reflects Monaco’s tradition of finely produced religious commemoratives. Highly collectible among thematic collectors of religion, Vatican-related subjects, and Marian philately, this stamp represents mid-century European sacred art in postage form.