255 Subfield $d - Statement of zone:

Subfield $d contains the statement of zone for celestial charts.

In records formulated according to ISBD principles, subfield $d data, along with any subfield $e data, are enclosed in parentheses.

Examples:

255 ##$aScales vary$d(Zones +90° to +81° to 63°, -81° to 98° ;$eeq. 1950).

255 ##$aScale 88 mm per 1°$d(RA 16 hr./Decl. +30° ;$eeq. 1973.50).