Hi Mario, The oldest "Ivory Diptych" or 'tablet dial' from Nuremburg that I am aware of was made by Lienhart Gresel in 1531. There were earlier ones made of wood some time in the 1480's.
I found this information in a book about the sundial collection of Harvard University (Cambridge MA, USA). The book is called "Ivory Diptych Sundials, 1570-1750". It is a "Catalogue of the Collection of Historical Scientific Instruments, Harvard University". Published 1992. Harvard has 82 iIvory diptych (tablet) sundials. The book is distributed by the Harvard University Press. (I found your answer on page 35). It is a wonderful book that gives you a real feeling for just how these dials were used and describes the different types of hours used, the dial furniture and so on. What surprised me the most was the fact that they could also use the moon to tell time at night. I hope this helps! Chuck O'Connell [EMAIL PROTECTED]
