SHIELD WITH UMBILICUS-LIKE UMBO PROTRUSION
"Umbo - a cone or beehive like protrusion often at the center of offensive weapons such as ancient shields" Dictionaries
I did not investigate the following point. Perhaps you should and let me know what you find - the question is - DOES UMBO POINT TO UMBILICUS-LIKE?
In medicine umbo may denote an inward projection of the tympanic membrane of the ear.