Signedin circle at the center: IOANNES**LOMBARDELLVS**CASTELLANVS**MASSE
Inscribedpunched on upper and right sides of square: *QVADRATVM**GEOMETRICVM*
punched at the top of center circle: 1559
punched on alidade: *LINEA*FIDVCIAE*ET*REGVLA*ILLE*GRADVS*
FunctionA Renaissance engineering instrument to make angle measurements in the horizontal as well as in the vertical position. A pair of dividers and a plumb line were commonly used with such an instrument.
Published ReferencesEva Koleva Timothy, Lost in Learning: The Art of Discovery (Newburyport, MA: Athenaeum Publishing, 2010).