See this post of mine with photos of a bronze Edward VII 1902 coronation model half-farthing token, with St. George (and his horse) and the Dragon on the reverse. It's 15 mm. and weighs 1.5 grams. https://www.cointalk.com/threads/smol-greek-horsey-coin.358529/#post-4364330
This tiny gold coin is possibly the smallest modern machine-struck coin ever made. Guatemala 4 Reales 1860 Obverse: Rafael Carrera facing right / RAFAEL CARRERA P. DE LA R. DE GUATEMALA Reverse: Wreath / 4 REALES 1860 / 21 Q R Gold, 9 mm, 0.83 gm, 0.875 fine The obverse has "FRENER F." under the bust but it is hard to read. Jean-Baptiste Frener was a Swiss engraver who lived in Guatemala from 1854 to 1897. He worked at the mint in Guatemala City. The reverse "21 Q" is 21 Quilates (21 karat or 21/24 or 0.875 gold). The "R" is mint assayer Rafael Romaña. Many coin catalogs treat the "R" as a mint mark. The original value was 4 reales or one-half peso, the equivalent of one-half US dollar. The coin is close in size to the little California fractional gold coins. It is smaller than the US silver three-cent piece and the "Panama Pill" 1904 2-1/2 centavos. Rafael Carrera was a peasant and soldier who rose to power during the first part of the 19th century. He was President of Guatemala from 1854 to 1865 and managed to keep Guatemala independent of Mexico. He also instituted the coffee-growing industry there. Rafael Carrera died on April 14, 1865.
This George II 1729 Maundy silver penny and Victoria 1838 silver three-halfpence (minted for use only in the colonies) are each only 13 mm. in diameter.
During Spanish colonial times in the New World you had the 1/4 real as the smallest piece struck in America. I bet they were very easy to get lost when traveling