Gustav Stahl, the former German soldier who made an affidavit that he saw four guns mounted on the Lusitania on the night before it sailed from this port on its last voyage and who disappeared immediately after the affidavit was made public, was produced by Secret Service men before the Federal Grand Jury yesterday afternoon at a proceeding to determine whether Paul Koenig, alias Stemler, who is the head of the detective bureau of the Hamburg-American Line, and others unnamed, had entered into a conspiracy to defraud the United States Government. The fraud is not stated specifically, and the charge is a technical one that may cover a variety of acts. Stahl, who speaks little English, affirmed through an interpreter to the Grand Jury that he had seen the guns on the Lusitania. He was questioned for two hours and a half and told his story with great detail. As he was leaving the Grand Jury room he was arrested by United States Marshal Thomas B. McCarthy on a complaint made on information and belief by Assistant District Attorney Raymond H. Sarfaty that Stahl had committed perjury in his testimony before the Federal Grand Jury. Stahl was held in bail of $10,000 by United States Commissioner Houghton and locked up in the Tombs. Stahl was the only witness heard by the Grand Jury in the proceedings against Koenig. It was learned that Stahl had been in conference with Koenig before he made the affidavit, and that his affidavit had passed through Koenig's hands before it went to Ambassador Bernstorff, who submitted it to Secretary of State Bryan. The proceedings against Koenig were initiated to establish the charge that Koenig used improper influence to induce Stahl to make the affidavit. While Stahl was waiting in the Marshal's chamber in the Federal Building, after his arrest, for the arrival of Edward Sandford, a lawyer, of 27 William Street, who had been assigned to act as his counsel, he was asked, through an interpreter: "Would you be willing to spend twenty years in jail for your Fatherland?" "Make it a hundred!" he replied, in German, and then broke into a hearty laugh. Stahl is about 27 years old and slightly under middle size. He has a round, somewhat rosy countenance, dark hair getting very thin in front, and parted in the middle, dark-brown eyes and a small, closely-cropped dark mustache. He was calm and smiling, ready with his answers, and very insistent and emphatic in repeating that he had seen the guns on the Lusitania. He was neatly dressed in a dark mixed suit, with a new straw hat, a green tie on which was a stickpin with a dog's head in porcelain, brightly polished tan shoes, and lavender socks with scarlet-embroidered flowers. Following is the complaint on which he was held: Raymond H. Sarfaty, being duly sworn, deposes and says that he is an Assistant United States Attorney for the Southern District of New York.