Reprinted from yesterday's late editions

"What will I do for an encore?" asked Armand Hammer as he stood before a 2,500-year-old Olmec figure, having just taken the president's son, Chip Carter, on a quick tour of an exhibit of Mexican treasures that cost him three quarters of a million dollars to bring to the United States.

Hammer, who also was behind American tours of French Impressionist works and art from the Hermitage, is a man who probably won't wait too long for an encore.

But Wednesday the head of the Occidental Petroleum Corp. was enjoying his present coup with an opening night reception for more than 600 and a movable art feast between the Smithsonian Museum of National History and the Hirshhorn Museum and Sculpture Garden.

Double-decker shuttle buses, supplied by the Smithsonian, carried the opening -night guests to and from the museum and the Hishhorn for the two-part exhibit spanning 12,000 years of Mexican art.

At the Hirshhorn, the saw the works of Mexico's modern masters, muralist-painters Orozco, Rivera and Siqueiros. Back at the Smithsonian Natural History Museum were the rare pre-Columbia treasures, many of which never have been seen in this country before, and works of Mexican artists four centuries after the arrival of the Spanish.

While President Carter was in Brazil Wednesday, his son Chip came to the Mexican exhibit but had only a chance for a quick look at the treasures because of guests who wanted to shake hands.

By sending his son to the opening as his personal representative, President Carter was showing his deep interest in Latin America, said Alejandro Orfila, secretary general of the Organization of American States.

At the dinner Wednesday, Hammer announced that the exhibit has been extended for two weeks even before it opens.It will stay in Washington until May 15 before going toNew York and Los Angeles