BRUSSELS — Dozens of diamonds spell out two giant letter T's next to the Stars and Stripes and “1776” and “2026.” Dozens more frame the numbers 45 and 47 in the shape of Superman’s logo. A diamond-winged eagle carries a ruby shield and clutches an olive branch of emeralds, below a radiant “250” and atop the phrase “250 YEARS USA” etched in 18-karat gold.