The 90% silver coins less than a dollar all have a weight and silver content exactly proportional to their face value, but the silver dollar has slightly more silver proportionally. You can count the total face value of a pile of American 90% silver coins (except silver dollars) by just weighing the pile and dividing the weight in grams by 25. Provided of course that they aren't badly worn.Every coin book has the weight, percentage, and a picture of each type of junk silver coin. And I think the denominations are proportional or am I wrong? Like a dime actually has 1/10 as much silver as a silver dollar. And the silver dollar is about 3/4 of a silver ounce. And they look and sound familiar. them
So for the smaller coins there is 25 grams total weight per dollar, and .7234 Troy ounces of silver per dollar.
For the silver dollar, it is 26.73 grams per dollar, and .7734 Troy ounces of silver per dollar (close to 3/4 of an ounce like you said)