
A large triangle points upward, its tip just below the top of the rim. Its lines divide at the centre into a fan rising to the tip and a fan opening down to the base, and two concentric circles surround the centre. The plotter drew the lines in pen, and I added a few highlights by hand in pencil.
One of four Meridian drawings. All four are built on a circle of evenly spaced points: chords between the points form a star polygon, and fans of lines gather at points on the vertical axis.