Gun Metal
Humbrol Authentic Colour MC23
Humbrol MC23 »Gun Metal«, the colour of wrought iron, compared to Tamiya X-10 »Gun Metal«, the colour of blued steel, and our own wrought iron »Gun Metal« mixture of 4 parts Vallejo 71.063 »Silver« and 1 part Golden 1040 »Carbon Black«.
Humbrol MC20 »British Equipment Grey« is a non metallic metal (NMM) equivalent of wrought iron.