Rattling egg

[BreeShu]

Found a egg today that sounds dry with a hard object inside. To preface, my hens don't like laying in the main house, young roosters keep making a mess of the nesting boxes. A couple weeks ago I made a heated box outside of the roost. They all love it and the eggs don't burst before I get a chance to collect in the evening. It really hasn't been long since I put the box out. What would cause the egg to sound so dried out inside? Without cracking it, is it likely another egg inside, or is there a chance it really did dry out and it's yolk I hear rattling?

 

[GodLovesU]

I’d say it’s another egg inside, OPEN IT!