In the ancient world, if you wanted to sign something you used a seal. They came in various shapes and sizes – stamps, seals, signet rings – but the general idea was always the same: you had a small object that you could press into clay or wax to mark it with a design unique to you – just like a signature. This could be used in various ways. In the Near East, for example, legal decisions or transactions might be recorded on a tablet, and then all the witnesses would press their seals into the clay next to their names. In other cases it could function as an official lock – a door or container-lid could have a blob of clay pressed over the join and this would be marked with an official’s seal. If the clay was broken – or if it had been replaced with one without the seal – then people would know it had been tampered with. Here’s one of the most famous examples of this: the unbroken clay seal on the tomb of Tutankhamun, photographed before it was opened in 1922.