A former director of the Bureau of Engraving and Printing was found guilty by a U.S. District Court jury yesterday of a conflict-of-interest charge that he gave favorable treatment to a private firm's proposal for a government contract after he had arranged for future employment with that same company.

James A. Conlon, 59 faces up to two years in jail and $10,000 fine. Judge Louis F. Oberdorfer, who presided at Conlon's trial, scheduled sentencing for Sept. 12.

Conlon left the Bureau of Engraving and Printing in July 1977, and immediately assumed the presidency of a subsidiary of the American Bank Note Company. In an indictment, a U.S. grand jury had charged that, from December 1976 to June 1977, Conlon negotiated and arranged for a job with that firm and at the same time supported its proposal to supply the bureau with an anticounterfeiting system to be used for U.S. currency.

The law that Conlon was accused of violating forbids federal employees from participating in decisions that involve prospective employers while they still are working for the government.

Conlon testified that he was involved in negotiations for employment with the subsidiary in early June. The government contended that he subsequently wrote a letter to the Federal Reserve supporting the purchase of an anticounterfeiting system from American Bank Note.

At the time the letter was written, Conlon still was a federal employee. He left the Bureau on July 1, 1977, the day he was named president of the bank note subsidiary firm.

Conlon admitted in court that he sent the letter but he testified that it was intended to save the government millions of dollars by securing the most cost-effective means of obtaining that equipment.

Attorney Plato Cacheris, who represented Conlon, said yesterday that he would ask Oberdorfer to set aside the verdict because it is contrary to evidence in the case. Otherwise, Cacheris said, he will ask the U.S. Court of Appeals to review the case.

Last October, Oberdorfer dismissed the conflict-of-interest charge against Conlon, ruling that the government had failed to explain exactly how it believed Conlon had violated that statue.

The federal appeals court last April reinstated the charge against Conlon, saying that the indictment was sufficiently specific. The appeals court also upheld Oberdorfer's decision to dismiss three perjury charges against Conlon because they were vague.

Conlon's former assistant director at the bureau, Richard C. Sennett, pleaded no contest last year to a similar conflict-of-interest charge also involving a subsidiary of the American Bank Note Company. A federal judge sentenced Sennett to pay a $500 fine and placed him on a year's unsupervised probation.