Legend (AGOL_Historical_Maps)

Epoch 8: 1970 - 1986 (Part) (6) High : 1 Low : 0 Epoch 7: 1972 - 1990 (Part) (7) High : 1 Low : 0 Epoch 6: 1961 - 1989 (Part) (8) High : 1 Low : 0 Epoch 5: 1952 - 1986 (Part) (9) High : 1 Low : 0 1975 - 1992 (Part) National Grid (15) High : 1 Low : 0 1965 - 1992 (Part) National Grid (16) High : 1 Low : 0 1959 - 1991 (Part) National Grid (17) High : 1 Low : 0 1952 - 1992 (Part) National Grid (18) High : 1 Low : 0 1948 - 1991 (Part) National Grid (19) High : 1 Low : 0