If I may I would add one little detail about this interesting contribution on better understanding of what the heck in Europe we deal with eggs (I did the same when I lived in Boston MA, and I make an inroduction on terms and measures in every cooking class when USA or UK recipes are involved).

For the Italian law
the difference between eggs belong to Cat A and Cat A extra
is not about the size, nor the weight.
Only the yolk size matters. So, in an egg industry must measure the gap between the inner side of the egg shell and the outer side of yolk .

This gap is filled by eggwhite, less important compared yolk.
If the gap is 4-6 mm you have Cat A
if it is less than 4 mm you have Cat A extra

I hope I wasn’t to boring.
For my job I recently attended some Nutrition and Hazard Analysis and Critical Control Points and I found several facts very interesting about food I’ve never thought about.

I’ll follow your feed. Ciao!