The first line is no longer extant. It appears in a photograph of the item from the 1930s. In C.S. Coon's notebook his rough drawing of the inscription also includes all four lines. However, a later drawing of the inscription in the Semitic Museum archives (probably by Thompson) is also missing the first line, and so the fragment containing it may have been lost for decades (or may never have left Ṣanʿāʾ). (From Huehnergard).
Huehnergard, John 2000. Old south Arabian inscriptions in the Harvard Semitic Museum. Pages 196-206 in Lawrence E. Stager, Joseph A. Greene and Michael D. Coogan (eds). The archaeology of Jordan and beyond. Essays in honor of James A. Sauer. Winona Lake: Eisenbrauns.