THE DESIGN ON THE BACK OF THE COVER is from the "Heptameron of Petrus de Abano" who was a magician and medical doctor in Italy in the late 13th century.
The manuscript from which this seal comes is a 17th century copy in the British Museum: Sloane 3850 ff 13b - 23.
The seal itself is that of the Sun. It forms the basic type for all the planetary seals of this work by d'Abano. In the center circle and ring, the one with the cross, are the words: Agla, Eloy, Adonay and Tetragrammaton. Inside these are "Alpha" --- name of the first letter of the Greek Alphabet, and the infinity symbol. The two outer rings list the names of various spirits of the planet (here spirits of the Sun) and the mark of the Archangel (in this case Michael). For the other planets, the inner ring and circle are the same but the names in the outer two rings and the Archangel's mark are those of the particular planet.
This solar seal can be used to work any spell that has to do with the Sun. It is of value in rituals and spells for gathering strength, for general health improvement (not for serious illness or injury), for masculine beauty, for gaining honor and for any general working on Sunday, the traditional day of the Sun. Note that the four names in the inner ring are almost the same as the divine names used in the Lesser Pentagram Ritual of the G.'.D.'., of O.T.O. and of A.'.A.'.