255 Subfield $a - Statement of scale:

Subfield $a contains the entire scale statement including any equivalency statements. Vertical scales or vertical exaggeration statements for relief models or other three-dimensional items are also included in subfield $a.

In records formulated according to ISBD principles, subfield $a includes all data up to and including the semicolon ( ; ) when subfield $a is followed by subfield $b.

Examples:

255 ##$aScale not given.

255 ##$aScale [ca. 1:90,000].

255 ##$aScale [1:6,336,000]. 1" = 100 miles. Vertical scale [1:192,000]. 1/16" = approx. 1000'.

255 ##$aScale not given ;$bConic proj.