The term "piccolo" on a tunesheet is normally used to describe
movements which play music with emphasis on the higher pitch treble
notes.  Those boxes are made from 1865-70 onwards and have a separate
smaller higher pitch treble comb.  Later in time the term was also
used for boxes with a single comb but with more use of treble notes.

Sometimes you come across a single comb type which was made to look
like the earlier 2-comb type by making a slit in the comb steel which
is only half the thickness of the steel; the makers became very
economical in later years.

The term "zither" is used to describe the use of a roll of thin
paper lowered on too the comb to create a buzzing effect.

Niko Wiegman
Netherlands