Mitsubishi Montero and Diamante vehicles with factory keyless entry systems used a family of remote keyfobs with FCC ID E4EG8D-522M-A from 2000 up until 2003 and on through 2006 for Montero. These remotes had 2, 3 or 4 buttons. These remotes are user programmable.
See the remotes with FCC ID E4EG8D-522M-A at this link.
Caution: When buying a replacement Mitsubishi car or SUV remote, never select your part on the basis of looks alone. Mitsubishi used several different families of remotes that look identical but are not interchangeable. Be sure to match the FCC ID of your original remote with the replacement keyfob or search Remotes Unlimited website by make, model and year of your vehicle or by the Mitsubishi part number.