Bill,
Roger is,as he said, one of the engravers I mentiomed at page 2,and his friend is the other. I believe Claus Willig is still living, I regret never having met him, in spite of visiting Recknagel in Schwienfurt many times.I believe, however,your search should be concentrated in and around Berlin.Also I believe that if the engraver is identified, it will be by the figures.Like Roger said, the training led to many similarities,but the differences in artistic talent shows up clearly in the figures.
Mike