Medieval manuscripts call this instrument the navicula (Latin for little ship) because of its ship-shaped design. We don't know for sure when and where the navicula was invented, but John Whethamstede, Abbot of St Albans (d. 1465), says that it was invented by a monk at Glastonbury Abbey. All the medieval naviculas and all the manuscripts about how to make and use them are from England, suggesting that the instrument was invented there.
New name, new design
In the early 15th century a manuscript about the navicula went to Vienna, where it was renamed organum ptolomei. It was studied and redesigned by the famous mathematician Georg von Peurbach (1423-1461), and the new instrument was printed by Regiomontanus in his book Kalendarium in 1476.