Maybe this will sound silly for those of you who had the opportunity to get in touch with metal typesetting but...
While reading Meggs' "A History of Graphic Design", on page 81 (3rd ed.), he describes the book Teuerdank, printed by Johann Schönsperger with type designed by Vincenz Rockner in 1517. According to Meggs:
Rockner carried this design quality [the quality of Rockner's fraktur compared to Gutenberg's textura] even further in a heroic effort to duplicate the gestural freedom of the pen. As many as eight alternate characters were designed and cast for each letterform. These had sweeping calligraphic flourishes, some of which flowed deep into the surrounding space. Other printers insisted that these ornamental letterforms had to be printed from woodblocks, for they refused to believe that it was possible to achieve these effects with cast metal types. (An inverted i in the 1517 edition, however, conclusively proves that metal types were used to print Teuerdank.)
After reading this paragraph two questions came to my mind:
1. If it wasn't for the inverted i, telling the difference from a woodblock print or a typeset ornament wouldn't be possible? Isn't it possible to tell the difference between these two techniques of printing just by looking at the printed piece? The thickness of ink, the irregularity of the shapes or something like that?
2. How was it possible to set those flourishes in metal type? Were they a whole piece of metal or maybe divided into several smaller parts put together?
If you don't have Meggs' book nearby you can read about Teuerdank and take a look at some pictures here: http://special.lib.gla.ac.uk/exhibns/month/feb2005.html
Anyway, it's impressive...