A: Harpocrates sitting to left on the back of a crocodile. His knees are drawn up and he is holding a was-scepter with both his arms in front of his body. On the top of the head the solar disk. Around Horus: a scorpion, a scarab, an ibis, an uraeus and a falcon.
B: Inscribed in three lines: ιαω|σαβα|ωθ → Ἰάω, Σαβαώθ.
A praxis known from a papyrus (PGM LXI 1-38) specifies that love charms had to be incised with the image of Horus on a lotus flower and the magical name Abraxas. The scheme represented on the gem is a descendant of the Horus on a lotus flower scheme.
Bibliography
Michel, BM on CBd-543
The British Museum Collection database on CBd-543