Ending a 10-month, high-publicity clash with police and county authorities, the Progress Club, Inc., yesterday pleaded no contest to charges of running an illegal gambling house and agreed to shift its focus from card playing to other activities.

Under a plea bargain agreement reached with Montgomery County prosecutors, the exclusive 400-member club agreed to back social, recreational and charitable activities instead of sponsoring the widespread card playing that has netted the club millions of dollars since it was founded in 1917.

Montgomery County Circuit Court Judge William Miller, accepting the terms of the plea bargain agreement, fined the club $500 and placed it on 18 months of unsupervised probation.

The no contest plea allows a judge to sentence a defendent without a conviction or a guilty plea.

Last December Miller declared a mistrial after members of a jury said they were too divided to judge the Progress Club despite a high-profile, four-day trial.

Miller's declaration left club members and prosecutors unable to claim a victory and both sides vowed to continue the fight.

At a press conference yesterday after the 15-minute plea hearing, State's Attorney Andrew L. Sonner said that club lawyers had asked for a plea agreement shortly after the trial ended.

If individual club members continue to play cards in informal groups such as those at country clubs and in private homes they will be doing so "at their own peril," Sonner said.

"The settlement of this case should end the public confusion which has surrounded the prosecution and defense of this case," Sonner said.

"It has never been the policy of the state's attorney's office to prosecute social gambling or private card games. The manner in which the Progress Club operated, however, amounted to its conducting an illegal gambling business, which of course could not be condoned or tolerated."

Meyer Bobrow, a club officer and 38-year member, told reporters, "We at the club did not realize we were not cooperating with the state law."

Most members, Bobrow said, "want to put it behind us, play a little bit of cards and get back to our charitable work."

According to trial testimony, the main activity at the club, now located behind a shopping center on Rockville Pike, was card playing.

More than $22,000 from club coffers and $8,000 from members was seized by Rockville police last June 5 in a late night raid that culminated a 5 1/2 month undercover investigation of the club.

All but $2,500 of the seized money is being forfeited to the city of Rockville under the plea bargain agreement.

Rockville police also will make periodic, "unannounced" vists to the club and city finance officials will examine the club books during the probation period under the plea agreement.