The key for the measurement system associated with the locale.
The corresponding value is an NSString object containing a description of the measurement system used by the locale, for example “Metric” or “U.S.”.
Available in Mac OS X v10.4 and later.
Declaration Syntax Version Information- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)