Link to Wartburg Foundation

Wikipedia article for Gittern

Sound sample and build process on YouTube

¡Ay triste, que vengo! on gittern

Detailed paper on the Wartburg Gittern (paywall)

Since 1860, the collection of the Wartburg Foundation in Eisenach has housed a small lute-like instrument that, based on the glued-in instrument label, is attributed to Hans Ott in Nuremberg, dated around 1450 and described as a gittern. This so-called Wartburg gittern has, to date, been considered to be one of the oldest surviving European plucked string instruments, is regularly mentioned in musicological literature and has often been ‘copied’ in the course of historical performance practice.

Edit: bottom two images are made by me, top image is from the Wikipedia article - color corrected to match my photos.