The string specifications on this chart are based on Bow Brand Gut harp strings. I use their “standard” gauge for most modern (post 1935) pedal harps, the “Lever Harp Gut” for Erard Gothic harps, early American harps (L&H, Wurlitzer, late Browne’s etc). These Lever harp strings are a close match for the Lyon and Healy string gauges that were dated 1911. They are also very close to the 1829 Erard string gauge that was used for late Grecian harps and the entire Gothic series.
There is some flexibility in these specifications. Grecian style harps in excellent condition can use the Lever harp gut strings. Gothics in excellent condition can use the standard gauge gut strings, but I strongly recommend against using steel-core wire strings on any antique harp, especially those from Europe or based on the Erard designs.
The specifications for “one octave light” and “Two octaves light” are based on modern standard gauge strings. The strings that are too thin for even the lever gut set are from Gamut Strings, a company that specializes in providing strings for historical instruments.
The special wire strings specified are available from Vermont Strings. They have consistently produced strings of excellent quality and reasonable price. The fiber-core wires sound so much like gut strings that the transition from gut to wire is virtually imperceptible. Using these strings in lieu of modern steel-core wires will result in a substantial reduction in overall stress on the harp and the harpist.