NMI DF.1945-122 is a kind nowadays referred to as an “early Irish harp”. The strings would have been of metal, probably brass wire. (the harp has some strings on it, of copper alloy, though these may be 19th or 20th century display strings and not for musical use).
If this harp was owned and played by Rose Mooney (1740 - c.1798), then we would have the tuning schedule as well as repertory that was played on it.
The tuning and sound of Rose Mooney’s harp is described by James MacDonell:
Rose Mooney’s had thirteen strings below and eighteen above the ‘sisters’. ... it was light, sonorous, and much superior to Quin's harp. „
James MacDonnell’s description above suggests that Mooney had 33 strings on the harp, probably with a tuning from GG in the bass (2 1/2 octaves below middle c) up to d''' (2 octaves and a note above middle c), with no string for the lowest F, and two strings for g below middle c.
Edward Bunting collected tunes from Rose Mooney, the only woman harper to attend the 1792 Belfast harper’s meeting. For my list of tunes collected from Rose Mooney, please see my Rose Mooney tunes page.
If this harp was owned and played by Turlough Carolan (1670-1738) then we have a great number of songs and instrumental tunes which are said to have been composed by Carolan.