The Livonian Diet was a meeting of the landowners of Old Livonia and their estates, which was also the highest legislative and judicial authority in Livonia. In 1422, at the Diet held in Valga, a general land code was adopted, which dealt with the basic norms of Christian society and certain matters of church organisation.
The figure of the cross interwoven with an ornament of a lily and pear branches on the stamp symbolises the consistent, steady growth and spread of the Christian way of thinking in the Middle Ages. The motif of the figure comes from the relief carved from dolomite above the door of the southern vestibule of the Karja St. Catherine’s Church. Paintings of the choir vault of this church are used on the edges of the stamp block, which consist of symbols with meaning, arranged in a circular ensemble according to a specific iconographic programme. Thus, on the main east-west axis, there is a woven cross (the divine harmony of the universe) and a pentagram (Christ as a perfect person), and on the less important north-south axis, the so-called legged devil, a triskelion, and cruciforms with acanthus leaves.