Easco Corp., a Baltimore tool and steel products manufacturer, reported the first annual operating loss in its history last year, despite a 9 percent increase in sales from 1983.

Easco said it had a net loss of $9 million ($1.26 a share) for the year ended Dec. 31, compared with profits of $10.2 million ($1.52) for 1983. Sales increased from $510 million to $571 million.

Easco officials blamed the loss on new-customer start-up expenses in the hand tool group, a second-half adjustment of tool inventory levels, and the cost of realigning certain facilities.

For the fourth quarter, Easco reported a loss of $3.4 million (47 cents) on sales of $147.3 million. In the fourth period of 1983, the company posted a profit of $1.9 million on sales of $132.1 million.

* Earnings more than doubled last year at Biospherics Inc., a Rockville supplier of high technology products and services to the health and maritime industries.

Biospherics said net income for the year ended Dec. 31 totaled $110,325 (2.8 cents) on revenue of $6 million, compared with $51,701 (1.3 cents) on revenue of $5.4 million in 1983.

Fourth-quarter earnings rose to $38,797 (1 cent), compared with a loss of $32,864 (0.8 cent) in the year-earlier period.

* Federal Realty Investment Trust of Chevy Chase reported a 28 percent gain in net income for the year ended Dec. 31. Profits totaled $10.3 million ($1.55), compared with $8 million ($1.37) in 1983. Revenue was up 29 percent, to $27.3 million from $21.1 million in 1983.

Federal Realty President Steven J. Guttman attributed the record results to higher rental income from the trust's shopping center and apartment investments.

* Net income for January was down at Potomac Electric Power Co., compared with earnings for the first month of 1984. Earnings for the one-month period ended Jan. 31 were $11.5 million (22 cents), compared with $13.2 million a year earlier.

For the 12 months ended Jan. 31, Pepco reported profits of $166.5 million ($3.19), compared with $145 million ($2.76) for the year-earlier period. Operating revenue was up slightly, to $1.19 million from $1.17 million for the year-earlier period.

* Smithfield Foods Inc., the Arlington-based packer of fresh and processed meats, said net income for its third quarter ended Jan. 27 rose 33 percent to $2 million (70 cents) on sales of $189.3 million, from $1.5 million (47 cents) on sales of $139.5 million in the comparable period a year earlier.