The outer shell is interesting, you mention that it was rubbery. I would have thought it might feel crusty.
An egg within an egg is called “counter-peristalsis contraction”. This is caused by a new yolk being released while an egg is already being "made" but has not yet been laid. When this happens, there is contraction in the oviduct that pushes the first egg back up the oviduct and they both travel back down together.
With yours, it's almost as if this happened more than once? Since it has layers it's been in there a while. Has your hen been acting normal?
If this is a one time glitch or she's a new layer, she may work the kinks out. I would keep watch on her for a few days regardless. There is really nothing that can be done, but I would worry that this may be a signal that she might have some reproductive problems in the future. Internal Laying where egg yolks, albumen and even whole shelled eggs are dropped into the abdomen is called reverse peristalsis. In this particular instance, your hen was able to pass the egg instead of it completely traveling back up the oviduct and into the body cavity.
fwiw - Lash Egg or Salpingitis is an infection of the oviduct. This is thick layers of caseous exudes. At first that's what came to mind for me too, but looking closer at the photos I see where it's layers of what looks like soft shelled egg.
Very interesting for sure.
tag in a few other to take a look see
@Eggcessive @coach723 @rebrascora @staceyj
