Graphic representation of the periodic table of chemical elements designed as a series table with Group 0 placed in the middle of the table. This table was originated by Curt Schmidt in 1918 and classified by chemist Edward G. Mazurs as Type IIC2-5 in his seminal work Types of Graphic Representation of the Periodic System of Chemical Elements (1957). This table appears as Figure 55 on page 126 of Mazurs' 1957 publication.
Schmidt, Curt, and Edward G. Mazurs. “Series Table with Group 0 Placed in Middle of Table.” Glass, circa 1918–1957. Edward G. Mazurs Collection of Periodic Systems Images, Box 1. Science History Institute. Philadelphia. https://digital.sciencehistory.org/works/vm40xs148.