Brutalist Ring in Sterling, most probably European ca. WW2

From 1947-49, my mother was a civilian working in MacArthur's Occupation Forces. Her photos testify that Tokyo was in rubble heaps, and rife with street urchins. In general, the Japanese were near starving, having given their all to an emperor who had been, until recently, a god. (Showa-tenno, "Child of Heaven Emperor," was known by his common name, Hirohito. After publicly renouncing his divine authority in 1946, he fully cooperated with the U.S. Army and is credited with Japan's smooth transition from monarchy to democracy. He was exonerated of War Crimes.) In 1947 the exchange rate was thousands of yen to the dollar, and my mother spent part of every paycheck on things that the Japanese, or European refugees (mainly German Jews like Eta Harich-Schneider, who taught my mother piano in her salon, once a week, and also taught at the royal palace), had managed to hang onto all through the war, until now, when defeated, desperate, and hungry, they were pawning them for rice money. The scenario was straight from a Marlene Dietrich song. ("Black Market," purred Dietrich. "Coo-coo clocks and treasures, thousand little pleasures... You like my first edition? It's yours; that's how I am. You see, in my position, you take Art, I'll take SPAM.")
A jewelry hound with eclectic tastes, Mom bought everything from carved jades to Netsuke to this ring, which came from and was made by? If you have any notion, please clue me.
I'm pleased to say that I have repatriated the most valuable of the Japanese things I inherited, after living with them in guilt all my life.