Shirley Sislen of the Mindel-Small real estate office in Bethesda was named one of the 20 top realty sales agents in Montgomery County last year, according to broker Robert J. Small.

William Barrett has been named co-ordinator for Nationwide Find-a-Home Service in the firm of Chris Coile & Associates, Inc., which has eight offices in the Annapolis area.

Joseph C. Rodgers, third vice president of the Suburban Maryland Home Builders Association, was recently presented the President's award for his service to the group in matters of legislation and other activities.

The Producers' Council, Inc., will hold a construction marketing seminar March 23-25 at the Sheraton-National Hotel in Arlington. For information, call 667-8727.

Newly open in Arlington is the Valley Heights condominium development, with units priced from $17,000. Sun Life Insurance Co. of America is the developer.

Walker & Dunlop, a Washington mortgage banking firm, recently arranged the sale of a 49,770-square-foot industrial building in Terminal Industrial Park at Newington in Fairfax County. Hallmark Iron Works, Inc., bought the structure for slightly more than $1 million and financed a portion of the purchase price with an $800,000 tax-exempt industrial revenue bond to an institutional lender.

National Graduate University, based in the District, recently purchased the Old Dominion building in Clarendon to provide space for an applied research laboratory. Worth Gatchell of Rucker Realty was the broker for the sale of the five-story structure for about $350,000.

Century 21 realty brokers in this area reported a total sales volume in excess of $31 million in January, according to regional owner George F. Kettle.