As usual, most of the people at the 25th Annual Washington Antique Show preview dinner spent a great deal of time debating whether the pieces they had at home were better.

At the event last night at the Shoreham Americana Hotel, Smithsonian Secretary Dillion Ripley, former secretary of state William Rogers, White House curator Clement Conger and their knowledgeable wives were among the several hundred antique collectors. They roamed through early American silver, 18th-century English furniture, American weathervanes and other enticements.

Conger and his wife spent some time admiring the $75,000 English antique secretary mounted with brass figures from Glenn Randall of Alexandria. But they actually bought several pieces of Chinese export porcelain from Elinor Gordon, their annual antique show purchase.

Gordon said that Chinese export porcelain has gone up in price in the last three years more than either oil or diamonds.

Malcolm Stearns of Hobart House, who will appraise silver at the show on Thursday, said he thinks that the current high "meltdown" prices for silver may endanger some good pieces owned by people who don't know what they have.

"One man showed me some coin silver forks he was selling for salvage. They were very rare 1838 dessert forks worth considerably more than the $28 an ounce he could have gotten from a smelter [who would have melted them down for their silver content]."

One tankard Stearns was selling was priced at $1,000 an ounce. The tankard weighed 104 ounces.

Hinda Kohn, who is selling Arts and Crafts Period silver, and Japanese-influenced American silver, said she had to mark up her silver prices today to meet the steep rise in silver. Mary Jane Mockwart and Gail Matheson, cochairmen of the event, said the buyers seemed mostly interested in the higher quality pieces.

Some 44 antique dealers from all over the eastern half of the country are showing and selling at the show, which opens to the public today at noon. Show hours are from noon to 9:30 p.m. through Saturday and from noon to 6 p.m. Sunday.

Verbal appraisals will be given on jewelry today, on silver Thursday and porcelain on Friday. A loan exhibit of silver by Revolutionary and Federal period silversmiths of Maryland and Virginia is up for the entire show.

The Washington Antiques Show is sponsored by the Thrift Shop, which benefits the Child Health Center Board of Children's Hospital, the Children's Hospital National Medical Center, the Columbia Hospital for Women Clinics, the Hospital for Sick Children and St. John's Child Development Center.