Copies of an obscene letter attacking Audrey Moore (D-Annandale) have been received by some contributors to her campaign against incumbent John F. Herrity for the chairmanship of the Fairfax County Board of Supervisors.

The letters, one of which is dated June 8 and postmarked in Richmond, begin with "Dear Audrey" and end with "Sincerely, Jack Herrity." The letters, which have crude language and extreme sexual content, are signed with an 'X.'

"Obviously, it's someone who doesn't like me or Ms. Moore," said Herrity, who agreed with Moore yesterday to ask the county's prosecutor and federal postal officials to investigate. "I think it's probably somebody who's mentally unbalanced. All I can say is whoever put this together is not in control of his faculties."

"It's incredible, isn't it?" Janice C. Spector, Moore's spokeswoman, said of the letter. "Unless you've read it, you don't understand."

Fairfax Commonwealth's Attorney Robert F. Horan Jr. said he was contacted by Moore's office yesterday and would investigate the matter. Horan said he had not yet seen the letter and could not speculate on what state laws, if any, it may violate.

The letters appear to have been sent only to some of those people who contributed more than $100 to Moore's campaign, according to her office. Spector said Moore's office had received about five calls from people who had received them.

Candidates must disclose to the Electoral Board the names and addresses of anyone who contributes more than $100 to their campaigns, according to Jane Vitray, secretary of the board. Vitray said "a lot" of people ask to see the lists, but they must first sign a Freedom of Information Act request form or a receipt.

Lois Sharpe, a longtime resident of Falls Church, contributed $500 to Moore's campaign, according to Moore's latest list of contributions and expenditures.

"Well, I've never seen anything like this," Sharpe exclaimed, after checking her mail and finding the letter. "Well, nobody's going to believe it, but isn't it awful? A sick mind. Oh, my heavens . . . . "

Gary E. Shoemaker of Annandale also received a copy of the letter. He said his wife Cathy "just couldn't believe her eyes." Shoemaker, who has lived in Annandale for three years, said whoever sent the letter "obviously got our name from the contribution list."

While Sharpe said the letter would not affect her future contributions, Shoemaker said their $250 contribution may be their last.

"We didn't realize anything over $100 is public knowledge, so we might keep it at $99," said Shoemaker, a national account manager for the Amdahl Corp. "It's not Audrey's fault, but you hate to see your contribution cause something like this."