Because milk is mostly water, a gallon of milk weighs about the same as a gallon of water. There are 2 pints in a quart and there are 4 quarts in a gallon. So that makes 8 pints in a gallon. Now a gallon of water weighs 8 pounds and there are 8 pints in a gallon, so that makes a pint of water or a pint of milk weigh one pound.
There is a memory device that can be useful: “a pint is a pound the world around”.
Ten gallons of milk inside the milk can at 8 pounds per gallon puts us at 80 pounds. The can itself weighs about 8 pounds. To answer the question, those 10-gallon milk cans weigh about 88 pounds. Little wonder that those old-time farmers had back problems!
Ten-gallon milk cans were standard on farms for decades, until bulk tanks and pipeline milking machines came along. There was a milk plant or creamery within reach of most every farmer so he could take his 10-gallon milk cans there twice a day. Before rural electrification, most farmers did not have a means of cooling milk cans. The Amish still use the 10 gallon can.
There were two handles on the side with a compression lid. Some lids were umbrella flat tops drooping down over around the edges. Others had plug covers, with a depression handle. Cans were 25 inches tall and 13 inches in diameter. Antique stores sell them and they fetch an outrageous price on eBay and Amazon.com.
When I was a little tyke on that hill farm on Oak Grove Ridge in the middle of Crawford County, my Dad bought milk cans from Montgomery Ward for $3.90, lid included.
You will see 10-gallon milk cans at Cracker Barrel Restaurant and Old Country Store. Also, the Machine Shed Restaurant chain places them around for display. Some people will have paintings done on the milk can. Others will use the milk can as a stand for flower pots.