You say the telescope is signed with the name “Theodorus”. Interestingly, and at the risk of confusing matters, Wikipedia has “Theodorus” as the Dutch equivalent of the English and French “Theodore”. Welsh is “Tewdwr”. Is there a Dutch connection?
Did Theodorus actually make the telescope or does his name simply refer to the artwork? Does the type of art work give any clues to the telescope’s origin?
Blethyn mentioned above was baptized as Theodore, not Theodorus. However, “Theodorus” may have been used as a marketing ploy due to the popularity of telescopes in the Netherlands at the time.