I’ve done some estimates on value here, but I hadn’t worked out weight or size.
So, if a golden dragon is worth roughly 4/5 of a pound sterling, and the noble (which weighed around 9 grams, and had a diameter of 33-35 mm) was 1/3 of a pound sterling, then I would guess a golden dragon would be worth ~2.6 nobles.
OTOH, a group of replica coin makers are going for 14 grams, 45 mm.