Tower pound
From Free net encyclopedia
A Tower pound was a unit of weight equal to 5400 grains - approximately 350 grams and just over 3/4 of an ordinary (avoirdupois) pound. The British monetary unit is called a "pound" because it was originally a Tower pound of silver (worth about £38 today). The weight standard was changed to the Troy pound (5760 grains/373 grams) in 1528.
By comparison, the modern U.S. standard pound is the same as the avoirdupois pound which is equal to 7000 grains or 16 ounces (454 grams).
Strangely, the word "ounce" is derived from the Latin word "uncia" which means "one twelfth" and twelve just happens to be the number of ounces in the Troy pound rather than the sixteen in the avoirdupois pound.