A big boy! Very few measure 20" across. Heavy spun brass with rim rolled around an iron ring. The boss with gadroons with three acorns in the spandrels - a rare motif. The oak leaves around the rim are also rare, and the flowers inside them might just be a Tudor rose -- was it made for the English market? Little wear except for polishing, so it may have been used to reflect the candlelight as shown in the detail of a 1475 painting by the Housebook Master.
Details and more photos.