Mid 16th century AD. A substantial gold ring with swivelling bezel; the hoop D-shaped in section with high-relief foliage to the shoulders and discoid bezel frame; swivelling bifacial central panel comprising: Side A - central white enamel-filled skull surrounded by legend in seriffed capitals '+ KNOWE · THY · SELF'; Side B - armorial bearings including a heater shield with a chevron between three leopards' faces and a mullet to the centre, helmet with crest of a ram in profile, possibly the arms of the Parker family, Earls of Macclesfield. See Chadour, A.B. Rings. The Alice and Louis Koch Collection, volume I, Leeds, 1994, item 641 for type. 19 grams, 25mm overall, 20.50mm internal diameter (approximate size British V 1/2, USA 10 3/4, Europe 24.4, Japan 23) (1"). Ex Robertson collection; previously part the jewellery collection of a Rayleigh/Hockley gentleman since the 1970s. The arms 'Gules, a chevron between three leopard's faces or' was borne by the Parker family, with three successive Earls of Macclesfield assuming them. Similar arms are recorded in BL Harley MS 1424 for the Hayes family of Litley 'Sable, a chevron Argent between three leopards' faces Or' . The presence of the mullet at the apex of the chevron is a cadency mark indicating the use of the arms by the third son of the current holder. The Earls of Macclesfield included the famous astronomer, George Parker (circa 1695 – 17th March 1764), known as Viscount Parker. A fellow of the Royal Society from 1722 and its President from 1752, Parker constructed an astronomical observatory and chemical laboratory at his Oxfordshire estate, Shirburn Castle. He was an advocate of the then contentious plan to reform the calendar by changing from the Julian to the Gregorian calculation, which prompted widespread outrage and demands by the populace that they be given back the eleven days which had been removed from the calendar in order to bring it into line with the observable astronomical cycle. The phrase 'knowe thy self' is an (early Modern) English translation of the Greek ????? ??????? (gnothi seauton) and is one of the so-called 'Delphic maxims' which were inscribed in the Temple of Apollo in that city according to the early Greek writer Pausanias. The originator of the phrase is not known for certain, and there are advocates for many potential candidates including Heraclitus, Pythagoras, Socrates and Solon of Athens. It is perfectly possible that the phrase was already in common use at the time of its inscription on the temple. It remained a stock phrase (often in its Latin translation nosce te ipsum) throughout the medieval period and was used as an admonition to leaders not to be deceived by the flattery of their followers nor to follow the opinion of the multitude, but rather to be true to one's own reason. It was used by Thomas Hobbs in Leviathan to remind readers that knowledge begins with self-knowledge, with an understanding of one's own motivations and emotions. [A video of this item is available to view on TimeLine Auctions website.]Very fine condition. A large wearable size.