Hello everyone. Getting back into BT after awhile away and have just started to look at the MUL. I do have a question about unit availability. When an era is not listed what does it mean? I understand extinct for eras like the Dark Ages for older designs that have not been produced. But what about when an era is not even listed? I looked for the CES-3R Caesar and the listing only goes to the Early Republic. What about the eras after this?