Convert from marco [Spanish] to millimass unit

Unit Definition (marco [Spanish])
The marco is a traditional units of weight in various countries of Western Europe. In each country the unit equals 1/2 the unit corresponding to the English pound. Thus the French marc equals 1/2 livre, 8 onces or about 244.75 grams; the Spanish marco equals 1/2 libra or about 230 grams; the German mark equals 1/2 pfund or about 280.5 grams; and the English mark equals 8 ounces or 226.8 grams. The English unit was used almost entirely for measuring precious metals.

Unit Definition (millimass unit)
The millimass unit is a unit of mass equal to 0.001 atomic mass unit, used in physics and chemistry. This unit is also called the millidalton (mDa). The millimass unit is an SI unit, but its proper SI symbol is mu, not the older symbol mmu.