Captain Van Amburgh, in an affidavit for the Commonwealth, became much more positive than he had been at the trial. He now used a more powerful microscope and in addition he had had comparative photographs taken of Bullet III and one of the test bullets. He offered twelve pictures of each bullet in which the lands and grooves were separately photographed so that the enlarged pictures could be compared. “The facts which I have found from my entire investigation,” he asserted, “are so clear that, in my opinion, they amount to proof. I am absolutely certain that the Fraher Shell W was fired in the Sacco pistol. I am also positive that the mortal bullet was fired in the Sacco pistol.” His findings were confirmed by Merton Robinson, a ballistics engineer for the Winchester Arms Company. Robinson not only maintained that Bullet III had been fired from Sacco’s pistol, but rejected Hamilton’s argument that the mortal bullet and those found on Sacco were of a different date of manufacture. As for Hamilton’s photographic evidence to prove that the hammer in Vanzetti’s revolver had not been replaced, it would have been quite possible, Robinson asserted, for an expert repairman to have inserted a new screw, or to have removed and replaced the old one, without leaving marks on the screw head. * * * * * On March 8, 1923, after much persuasion on the part of the McAnarney brothers, William Thompson agreed to enter the case for the limited purpose of arguing the motions for a new trial. He had been hesitant about becoming involved, but, ironically enough, it was Katzmann’s attack on the integrity and qualifications of Dr. Hamilton that finally persuaded him.