Mike, In my youth we farmed acres of potatoes,these spuds were packed in 100wt =112 lbs;sacks.There were 20 of these in the english ton which =2240lbs. The ton U.S.A. = 2000 lbs;this difference in the designation of the ton has lead to some under estimating the the rating of English proof pressure marks. For example a British proof test marked 3 tons per square inch = 6720 pounds per square inch and not 6000pounds per square inch!

Roy Hebbes