This is useful for converting amounts from Stone to Troy Ounce and vise verse

t oz:

A troy ounce (t oz) or (toz) is a unit of measure used for weighing precious metals that dates back to the Middle Ages.

Originally used in Troyes, France, one troy ounce is equal to 31.21 grams, according to the U.K. Royal Mint.

st:

The stone is an English and imperial unit of mass now equal to 14 pounds (6.35029318 kg).

England and other Germanic-speaking countries of northern Europe formerly used various standardised "stones" for trade, with their values ranging from about 5 to 40 local pounds (roughly 3 to 15 kg) depending on the location and objects weighed.

The United Kingdom's imperial system adopted the wool stone of 14 pounds in 1835. With the advent of metrication, Europe's various "stones" were superseded by or adapted to the kilogram from the mid-19th century on.

The stone continues in customary use in Britain and Ireland used for measuring body weight, but was prohibited for commercial use in the UK by the Weights and Measures Act of 1985.

By the way, this app is useful for converting amounts from Stone to Troy Ounce and vise verse.