These are two incomplete sets combined to make almost a complete set (volume #10 of the Macropaedia is missing). There is a Macropaedia set and a Micropaedia set plus the 1985,1986,1987,1988,1989, and 1990 Britannica Book of the Year. Seven volumes of the Macropaedia set (red) are from a set published in 1980. The rest (black) was published in 1984.