23 - Form of item (006/06)
One-character alphabetic code that specifies the form of material for the
item.
# - None of the following
a - Microfilm
b - Microfiche
c - Microopaque
d - Large print
f - Braille
o - Online
q - Direct electronic
r - Regular print reproductionEye-readable print, such as a photocopy.
s - Electronic
| - No attempt to code