The next major redesign took place during the presidency of Richard Nixon, with the new model of Lincoln Continental unveiled in 1972.
Though it wasn't a convertible, the vehicle had opening roof panels if the president wanted to stand and wave to crowds from the vehicle while electioneering or on official visits. An extra quarter inch of armor was added, bringing its weight up to 5,000 pounds.
The vehicle was put to the test in two presidential assassination attempts, speeding President Gerald Ford from Union Square, San Francisco, after Sara Jane Moore narrowly missed him in a shooting in 1975.
Jimmy Carter also used the same model when he took over in 1977, as did Ronald Reagan from 1981.
That year, one of the six bullets, fired by would-be assassin John Hinckley Jr, hit the right window of the vehicle, and another ricocheted from its roof, seriously wounding the president. He later made a full recovery.