I am really interested to see that in your 3rd record's signature statement you have called the first leaf [A]² and assumed that the final leaf is probably [A]1. I have always struggled to understand how cataloguers make these judgements. What is the best way to ascertain that leaves are conjugate, rather than separate? How do you know whether [A]1 or [A]2 are retained? Is it mostly about presumption, or are there obvious signs? How would you describe the register if it had no printed signatures?