Meanings of proof gallon in English

On brandies, or other spirits manufactured or distilled from grain or other materials, one dollar and seventy-five cents per proof gallon.

Upon brandies, or other spirits manufactured or distilled from grain or other materials, one dollar and seventy-five cents per proof gallon.

The tax on legitimate whiskey is $2.25 a proof gallon which makes it prohibitive in a community competing with the moonshiner's untaxed product.

The proof gallons of spirits distilled during the year ending March 31st, 1893, were 10,691,576 in England, 20,107,077 in Scotland, and 13,615,668 in Ireland....