Three gunmen herded employes of a Connecticut Avenue jewelry store into a bathroom yesterday, then smashed open showcases and escaped with more than $200,000 worth of jewelry in what D.C. police called a well-planned robbery similar to one at a Georgetown jewelry store last month.

Police gave this account of the midday holdup:

Four employes and two customers were inside Charles Ernest Jewelers at 1027 Connecticut Ave. NW about 11:30 a.m. when a well-dressed man walked in and asked to see a diamond bracelet.

A store employe unlocked a showcase, showed the man the bracelet and gave its price as $675. The man said he would return shortly, walked to the door, and opened it.

As he did, two men emerged from the Connecticut Avenue lunch hour throngs, slipped into the store and drew guns. The first man also drew a handgun. The three forced the employes into a bathroom in the rear and barricaded the door. The two customers were left in the showroom area and ordered not to move.

Smashing open locked display cases, the men grabbed handfuls of gold and diamond jewelry, then seized about $2,000 in cash and more jewelry from an open safe before fleeing.

No injuries were reported. In the earlier Georgetown robbery, one man was injured as items valued at $200,000 were taken from the Jewel Boutique, 1250 Wisconsin Ave. NW.

In that robbery, which occurred shortly before noon on Monday, July 13, one man was admitted to the store, presumably to inspect jewelry he had seen there before. As he was opening the locked door, ostensibly to leave, he admitted three confederates, who joined him in tying up the store's employes and ransacking display cases.

The Georgetown robbers took diamond rings, gold chains and watches from the cases, and also removed jewelry from the street-display windows as passersby watched, police said. Two handguns also were taken, and the store's owner required hospital treatment after being struck on the head. No arrests have been made in either robbery.