System/Library/Frameworks/Foundation.framework
NSUnitDispersion.h
@interface NSUnitDispersion : NSDimension <NSSecureCoding>
@property (class, readonly, copy) NSUnitDispersion *partsPerMillion;
@property (class, readonly) BOOL supportsSecureCoding;
+ (void)initialize;
+ (id)icuType;
+ (id)baseUnit;
@end