Scope Inc., a Reston-based electronic company, reported yesterday a 20 percent increase in first-quarter profits.

At the annual meeting in the Dulles Marriott Hotel, stockholders also approved an increase in authorized common shares to 5 million from 2 million. It was the first time Scope held a stockholder meeting outside of New Hampshire, its state of incorporation.

Earnings in the January-March quarter were $908,000 (75 cents a share) compared with $755,000 (62 cents) in the 1978 period, as sales rose 29 percent to $15 1/2 million.

Scope has grown in the last five years from $21 million of sales in 1974 to $59 million last year, a compound annual rate of 29 percent. Earnings have increased in the same period from $566,000 to $3.7 million, a 60 percent annual growth rate.

Stockholders also approved a stock option plan, whereby options to buy up to 100,000 shares of common stock may be granted to officers and key employes.

One new director elected is Jonathan Gestetner, joint chairman of Gestetner Holdings Ltd., a unit of a London company that bought 321,000 shares-19 percent of Scope's outstanding shares-in February. Most of these shares were purchased from Scope founder and former chairman Richard E. Williams and his family. Williams resigned from the Scope board early in the year.

Scope is engaged in computer-related products and services, communications and material handling. Officials said a backlog of orders and contracts on March 31 was $17 million, about 50 percent above the same period last year.

There were these developments at other annual meetings:

Crown Central Petroleum

A substantial rebound in first-quarter profitability was reported by the independent oil company, at its annual meeting in Baltimore.

Chairman Henry Rosenberg Jr. said Crown profits totalted a record $16.2 million ($8.0) a share) compared with a loss in the 1978 period of $802,000. Sales rose to $217 million from $134 million.

There was an increase of more than 31 percent in the physical volume of products produced in the recent quarter compared with last year, when some Crown facilities had been shut down for repairs. Refinery operations in the 1979 period were at virtually full capacity.

At the time, the average price received for all products soared 24 percent. Rosenberg said the results do not necessarily indicated earnings for the balanced of the year.

Arundel Corp.

President Francis Knott told the stockholders' meeting in Baltimore that he will recommend to directors in June a resumption of dividend payments. The last payout was a 6 percent stock dividened in January 1974.

Arundel, a heavy construction and real estate company, also is pursuing an acquisition program into new lines of business in the Baltimore area, Knott said. He mentioned financial and insurance services, energy-related businesses and waste management companies as possibilities.

First-quarter operating profits declined to 72 cents a share from $1.43 in the 1978 period.

Phillips Morris Inc.

Meeting in Richmond, stockholders of Philip Morris approved a two-for-one stock split proposed by a directors in February.

Authorized common shares were increased to 200 million from 100 million and a new class of 10 million serial preferred stock was approved. New shares from the split will be distributed May 31 to owners of record April 27.

A. H. Robins Co.

First-quarter profits declined slightly but President Claiborne Robins Jr. told the annual meeting on Wednesday that he still expects 1979 earnings to exceed last year's levels. The pharmaceutical firm earned $8.68 million (33 cents a share) compared with ,$8.97 million (34 cents) las year as sales rose to $94 million from $89 million.

Robins also said capital expenditures would increase to $18.4 million this year from $12.6 million in 1978. Interally-generated funds will finance the expansion, he added.

Greater Washington Investors

At the annual meeting last week, Greater Washington announced plans to offer 1.2 million shares of stock in an attempt to recover from years of financial difficulties for the ventural capital company.

To rebuild the GWI capital base, President Don Christensen said, management was seeking authorization to sell new shares.

However, a majority of stockholders was not present to approve the sale, so that part of the meeting was postponed until next Monday. If stockholders reject the proposal to sell shares at $1 apiece, GWI "won't go out of business," but the company's position would be much improved if the offering can be made, Christensen added.

A $1 asking price would be a 17 percent discount from GWI's recent net asset value of $1.20 a share.