Hi! It's easy to candle an egg to see whether its a large egg or double yolked.
Double yolked eggs are not good for hatching (they can hatch, but that is unusual).
Since their hens are so prolific about producing double yolkers, (and if you want that), you could ask them for a dozen of the single-yolk eggs and raise your own double-yolkers.
I think getting a double-yolk is almost freakish --- my old 10+ year-old Barred Rock hens layed double yolk eggs sometimes and *I* thought (perhaps incorrectly), that their reproductive system was just slowing down/failing.
Those were the only double yolked eggs I've ever seen here (and now I candle every egg laid here because I'm odd about eggs).
Lisa
Double yolked eggs are not good for hatching (they can hatch, but that is unusual).
Since their hens are so prolific about producing double yolkers, (and if you want that), you could ask them for a dozen of the single-yolk eggs and raise your own double-yolkers.
I think getting a double-yolk is almost freakish --- my old 10+ year-old Barred Rock hens layed double yolk eggs sometimes and *I* thought (perhaps incorrectly), that their reproductive system was just slowing down/failing.
Those were the only double yolked eggs I've ever seen here (and now I candle every egg laid here because I'm odd about eggs).

Lisa