I wondered if "Guildo" was just a misreading of someone's
water-dribbled handwriting on a seed packet or similar,
and if the man's name was actually "Guido Pietroboni",
but a WWW search found no records under that name.
There is a place in France with Guildo as part of the name:
http://en.wikipedia.org/wiki/Saint-Cast-le-Guildo
The only person I found with the name Guildo is Guildo Horn,
a German stage performer, and it is a made-up stage name:
http://en.wikipedia.org/wiki/Guildo_Horn
(So, Google was not helpful here in guessing whether Guildo
or Guido would be correct for this variety.)