The State Department of Corrections may purchase the machinery and establish a plant for the purpose of manufacturing motor vehicle license plates and metal road signs. The charge for license plates and metal road signs sold to the Department of Public Safety and the Department of Transportation shall be in line with the prices previously paid private manufacturers and all state motor vehicle license plates, metal road signs, and other signs capable of being manufactured by such a plant shall be purchased through the Department of Corrections and manufactured by it. The Department of Public Safety may prescribe the specifications of plates and the Department of Transportation may prescribe the specifications of signs used, the specifications to include colors, quality, and quantity.