[null and void]

Did you mean the document is signed and then the seal is crimped into the paper over the signature?

It’s a lot easier, neater and more natural to sign on a smooth flat surface.

[palmer]

Did you mean the document is signed and then the seal is crimped into the paper over the signature?

Generally. But in the posted pictures (factcheck and authentic certs) the signature is just rubber stamped separately and they didn't both with a pen and ink signature underneath the seal. My point was only that they are both done (and only readable) from the back. And that was confirmed by Polarik.