eli5 Eggs in the supermarket state on the box “Double Yolk”. Without cracking them, how do they know….?

Question

Apologies if this is ridiculous and should be in no stupid questions but it just struck me

In: 2748

Answer 1

If you shine a bright light through the egg you can see through it enough to detect two yolks.

Also the double yolked ones always end up in the largest category when eggs are sorted by size, so they wouldn’t even need to check that many to additionally sort.