Wikipedia
Trett (or tret) was an allowance made up until the early 19th century, for waste, dust, and other impurity in items in commerce, generally amounting to 4 pounds in each 104 pounds (3.85%). It fell into disuse because merchants preferred to simply adjust the price, rather than make a calculation for trett.
Usage examples of "trett".
Recoil, who pioneered Operation Space, and two United States Army officers on the platform—Major James Ob-blington, formerly of Brooklyn, New York, now of Space, and Lieutenant Noble Trett, formerly of Sioux City, Iowa, now of Space.
In spite of the “sir,” Trett sounded curiously listless, almost insubordinate.
At first the three voices clashed and blurred, but the General, on a signal from the moderator, quit talking, and the conversation that ensued between Trett and Obblington was audible and clear.
Somebody shot at us there in that field and Trett or whoever he is ran off.
I pieced together a list of names from some torn papers Trett dropped on the plane and hello?
As the manacled spies were marched out in single file the lads from Bayport recognized the locksmith who followed Trett, and each of the others whom they had discovered on the Flying Express.