According to author Adrien von Ferscht, the central medallion beneath the monogrammed cartouche depicts three of the “babao” or “Eight Precious Things” (or The Eight Treasures), which are generally auspicious symbols of good fortune. They often occur as a complete or partial set as decoration on ceramics from the Yuan dynasty and are sometimes combined with other auspicious motifs. They also occur individually as porcelain base marks. Red ribbons makes each a charm. They are:

Jewel or "pearl"- associated with the granting of wishes
Cash coin - wealth
Open lozenge - used in ancient times to ornament a headdress, victory
Pair of books - symbol of learning and one of the Four Signs of the Scholar
Mirror (solid lozenge) - unbroken conjugal happiness and counteracts evil influences
Musical jade stone gong (Qing) - a ministerial emblem and a symbol of a just and upright life; symbol used alone in decoration as the homophonic word 'festivity' or 'celebration'
Pair of rhinoceros horns - happiness
Artemisia leaf - good luck and prevention of disease

For further information please see Adrien von Ferscht, Chinese Export Silver 1785-1940 – The Definitive Collectors’ Guide, 4th Edition, Glasgow and Beijing, January 2015.