Bill Bateman and Randy Schaeffer help keep the records for the 2,540 families who believe in -- and treasure -- the real thing, or anything that carries its name:

Bottles, caps, signs, trays, napkins, coasters, calendars, watch fobs, advertisements -- anything that bears the name Coke or Coca-Cola.

Bateman, 41, and Schaeffer, 33, both mathematics professors, are among the leaders of an international organization called The Cola Clan, which opened its ninth annual convention yesterday in the Hyatt Regency Hotel in Crystal City.

About 1,000 members of the clan, some from as far away as Japan and Germany, are on hand for the five-day event, drawn in part by the opportunity to gawk at some of the rare Coke memorabilia on display there, such as the three 1910 Coke calendars that Bateman and Schaeffer sold recently for $2,105.

It has been the pair's ability to find and sell memorabilia like that that has made clan members speak with reverence when they mention Bateman and Schaeffer.

"A great number of members of the organization depend on them for information," said Cola Clan President Pop Poppenheimer of Memphis. "Certainly they're the top folks in the field. They might not say that, but I certainly feel that way."

Bateman and Schaeffer, both of Kutztown, Pa., were in fine form yesterday afternoon, conducting an hour-long seminar on "Researching and Dating Your Collectibles" for about 100 of the Cola faithful.

"You wouldn't believe what their collection is like," said Sylvan Richter, 49, of Baltimore, to a woman in an elevator shortly before the seminar.

"I couldn't begin to guess," the woman replied.

Bateman and Schaeffer have used their research skills for 10 years to date and collect their more than 10,000 Coca-Cola items -- enough to rival the archives of the Coca-Cola Company in Atlanta.

Although the clan is independent of the company, it asked Bateman and Schaeffer to testify in a recent trademark infringement suit against a rival, C&C Cola, in New York. The case, however, was settled out of court before the pair were called to the stand.

The two men have traced Coca-Cola's growth since the turn of the century when rumors abounded about whether cocaine was in the drink. Although they say the company doesn't like them to talk about it, Schaeffer said that very small traces of cocaine sometimes would seep into the drink from the extraction process of the coca leaves used in making the cola syrup. By 1906 when the Pure Food and Drug Act passed, the process had been refined and the seepage was eliminated, he said.

Today it isn't easy to collect Coke items. There is the problem of counterfeiting. "People have been fooled for hundreds of dollars," said Schaeffer, recalling that he had warned a clan member not to buy a Coca-Cola carnival glass ash tray. It was a fake.

Being a serious Coca-Cola collector isn't a hobby for those with a thin wallet. A small advertisement from a 1905 magazine can fetch $150.

Bateman pulled out a small box of 43 Coca-Cola booklets from his hotel room's dresser. "I spent $200 on this little pile of books here. It's disgusting, but we want the information," Bateman said.

The two men go to great lengths to get it. They traveled to Watertown, N.Y., to purchase the 1910 calendars. While there, they decided to learn a bit more about a little-known actress who modeled for some Coca-Cola items around the turn of the century.

"To give you an idea of what type of lunatics we are, we checked out her gravesite," Bateman said.

But the thrill of investigation is part of the reason Bateman and Schaeffer continue their pursuits.

"Besides the beauty and value of this stuff, there's also the intellectual aspect of it . . . the investigating aspect of it. We're often asked why do you collect? There's no real reason for it," Schaeffer said.

"Once you're hooked," Bateman added, "You're hooked."