Washington's subway system was the locale yesterday for inauguration of a new business enterprise - express delivery of small packages and documents by Archer Courier Systems Inc.

Based in New York, Archer is engaged in local, national and international delivery of documents or packages in and between some 300 American cities and overseas points.

The company has been in business here for about seven years, and yesterday's introduction of delivery by subway is designed to take advantage of rapid travel time between downtown stations and between downtown and the Maryland and Virginia suburbs, according to President Stanley Katz.

Washington has become one of Archer's prime markets, and the company now employs about 75 persons here out of a nationwide staff of 800.

According to Katz, whose local operations also have moved into new facilities at 1625 I St. NW, media companies, advertising agencies, law firms and printers are among the largest volume users of Archer personal delivery operations.

Delivery by subway between downtown points carries a minimum price of $3.25 and the cost between downtown and Silver Spring, now the Maryland terminus for Metro, is $9.75.

In business for 19 years, Archer handles some 4,000 package a day with annual revenues of $8 million. The firm is open 24 hours a day, seven days a week.