Character position definition and scope:

A one-character alphabetic code indicates the base of the film.

Safety base film is a comparatively nonflammable film base that meets the standard requirements for a safety base.  On some film, the phrase safety base or a small equilateral triangle appears on the edge of microforms.  Some microfilm produced overseas has similar notations in foreign languages.

Vesicular and diazo microforms are always a safety base, as are silver halide microforms manufactured in the United States since approximately 1951.

Nitrate film base is a highly flammable film base that does not meet the requirements for safety base film.

A fill character ( | ) is used when no attempt has been made to code this position.

Record requirements for National-level and Minimal-level records:  Optional.

Guidelines for applying content designators:

Codes:

Descriptions:

  Safety base:

 

a

Safety base, undetermined  Safety base film whose type has not been identified.

c

Safety base, acetate undetermined

d

Safety base, diacetate

p

Safety base, polyester

r

Safety base, mixed

t

Safety base, triacetate

 

 

 Nitrate:

 

i

Nitrate base

m

Mixed base (nitrate and safety)

 

 

 All other:

 

n

Not applicable

u

Unknown  The base of film of the microform cannot be determined.

z

Other  A film base for which none of the other defined codes is appropriate.

|

No attempt to code

Content designator history:

b - Not safety base  [obsolete]:  Code b was made obsolete in 1991 when 007/12 for microforms was made consistent with the 007/12 (Base of film) for motion pictures and code i (Nitrate base) was defined.

To return, select:

007:  Microform

007  Physical Description Fixed Field