From the Robertsbridge Codex of circa 1325. Only three of the six puncti are reproduced in the version I'm playing (Historical Anthology of Music, ed. by Davison and Apel; Harvard Univ. Press, 1968).
If anyone has the full version and can send me as pdf, I would be very grateful!
Played as Blockwerk style, all principals and mixtues of GO and Pos; tuning Pythagorean.
Of course, no one knows how it should really be played. I used my own musical common sense as best as I could. Not sure if the tuning system is totally correct either, but it sounds even older than meantone.
I was in Belgrade's National Museum and they had 3rd C. A.D. Roman silver and ivory organ pipes on display which had been found in Serbia. This triggered my renewed interest in very early organ music.