Simplify the following text for a Grade 14 native English-speaking person.
Original: It has some limited use in the United States , most commonly in measuring the displacement of ships , and was the unit recommended for warships by international agreements between the world wars , for example battleships were limited to 35,000 long tons .
Simplified: It has some limited use in the United States , most commonly in measuring the displacement of ships , and was the unit prescribed for warships by the Washington Naval Treaty -- for example battleships were limited to a mass of 35,000 L.