Cf. Dalton, op. cit. (1912) pl. XXI nos.1448 & 1450 and p.126, nos. 814-819 (with hexagonal bezel) also Oman.op.cit,pl.85 B & C.
also D.Scarisbrick, Rings Symbols of Wealth, Power and Affection, London 1993, p. 68-69, also see Christie's catalogue, Rings From Antiquity to the Present Day, 5th Oct. 1988, lot 363 for similar ring.