The Metric System of Measurement is part of the International System of Units (SI), and was created in France at the time of the French Revolution in the 1790s. Since then, it has seen many changes, and has been widely adopted as the standard system of measure by most of the developed world. Since the system is used in many countries and languages, occasionally non-standard symbols are used. MQ is such a symbol.
What it Means
MQ is an Italian abbreviation that stands for “metro quadrato”, and translates as “square meter”. It is used to denote measurements of area. Similarly, the unit symbol cmq is square centimeters and kmq is square kilometers.
Where it's Used
This symbol may not be seen in any academic or scholarly publications, but may appear on some websites published in, or translated to, the Italian language. It is used colloquially in the same way that "sq cm" is used to mean "square centimeters" in place of "cm^2".
In 1875 most of the industrialized nations signed the Treaty of the Meter, which established The International Bureau of Weights and Measures (BIPM, for Bureau International des Poids et Mesures). This agency, located in Paris, presides over and maintains the standards of the International System of Units. To keep the system current and useful, as well as to review and establish standards and rules, the General Conference on Weights and Measures is held every few years by the BIPM with representatives from all industrialized nations, as well as members of the International Scientific and Engineering communities.
Rather than use the non-standard symbol MQ, or its relatives, the BIPM recommends following the rules established in the SI. Strictly speaking, abbreviations are not allowed, and should be replaced by their approved symbol counterparts. For example, instead of mq, use m^2.
The wide adoption of the policies and standards set forth by the International Bureau of Weights and Measures ensures that the Metric System, and the System of International Units will remain the global benchmark for measurements for the foreseeable future. As a result, there will probably be less and less non-standard symbols for units on the Internet and elsewhere.