This morning gathering eggs I found this in my OEGB pen. It's the smalest egg I've found. It's just a wind egg, but it's still small. It's in a 1/4 teaspoon and next to a regular OEGB egg.
we used to visit "Blooms chicken farm" and they would have eggs that had no yolks in them they were so small. it would be interesting to see if yours had a yolk in it.