Local egg was doubled yoke... It was a exceptionally big egg so the 2 yokes were big like an extra large egg would be.
Reading on line where double yokes are produced by young hens just starting out. Their egg laying systems are not synched where one egg should be released into the reproductive tract.
Got a baker's dozen this time ...
source of info ... https://www.backyardchickens.com/articles/double-yolk-eggs-all-you-need-to-know.77683/