These things are stupid rare. The bottom pot tended to be used as a flower pot and as such, no one had them.
I came across the top two pieces from a local lady who hated cast iron and just wanted rid of them… I sourced the bottom pot from a dude in a combo cooker group.
Definitely something you don’t see everyday.
Edit Here is the patent
Like the other fellow said… the middle one is a smaller pot. I added the patent to the original post… I tried to upload more photos but it’s timing out tonight. :/