Scope Inc., an electronics firm based in Reston, reported a third-quarter loss of $3.16 million on sales of $19.18 million compared with profits in the same period last year of $523,000 (43 cents a share) and sales of $16.32 million.

For the nine months ended Sept. 30, sales totaled $57.57 million compared with $51.58 million during the same period last year, a 12 percent increase. Scope suffered a net loss of $2.22 million compared with a net income of $1.65 million ($1.36) for the same nine months in 1980.

Scope officials attributed the quarterly loss to cost overruns on several contracts at the firm's MRC Corp. subsidiary and to "management's reclassification of two asset accounts on the balance sheets," which resulted in one-time charges of $2.61 million against income.

Government Employees Life Insurance Co. of Washington reported third-quarter operating profits of $2.1 million (47 cents a share) versus $2.13 million (48 cents) a year ago. Counting losses from capital transactions in both periods, net income fell to $2.06 million (46 cents) from $2.13 million (48 cents). Nine-month earnings from operations, not counting capital gains or losses, declined slightly to $6.05 million ($1.36) from $6.18 million ($1.39).

The Geico Corp. unit said recent results reflect higher policy terminations and benefit payments and expected start-up expenses for a new brokerage division. Individual life sales in the first nine months totaled $288 million, more than double the 1980 rate.

Eastmet Corp. of Cockeysville, Md., a metals manufacturing firm engaged primarily in the manufacture and marketing of flat-rolled stainless steel products, has reported a first fiscal quarter loss of $2.62 million on sales of $68.37 million. During the same quarter last year, Eastmet recorded net income of $670,000 (14 cents) on sales of $72.22 million. Eastmet's fiscal year begins on June 30.

According to a statement issued by corporation president George R. Walsh, the loss was "due to a reduction of orders and shipments" caused indirectly by "high interest rates, which are largely responsible for both discouraging capital investment and increasing the inventory carrying costs of distributors."