 Ten trains were built by Martin Marietta in 1969 at the cost of about $7 million USD each and they were used on the monorail system between 1971 and 1989 before they were replaced by the Mark VI monorail, although a few lasted until 1991.Sometime between 1991 and 1994 Monorail Coral and Lime (which had been introduced new in 1984) were sold for $3.5 million each, refurbished, and used to begin the Las Vegas Monorail operations.In 2004 Lime and Coral (now the MGM and Bally) were replaced by fully automated Bombardier MVI 4-car trains.