Wikipedia
Siffernotskrift
Siffernotskrift or sifferskrift is a form of numbered musical notation in which numerals are given which correspond to musical notes on given instruments. The system was devised and used by Swedish clergyman, psalmist, and music educator Johan Dillner (1785-1862) in the hymnal he wrote 1830 for the psalmodicon - a one-string, bowed string instrument.