I have to disagree with Rich. The brass fire extinguishers were the carbon tetrachloride type and were used in many soft skins and lighter AFVs (armored cars, halftracks). Some were one quart in capacity. There were many brands.
M7s and other larger vehicles (Light and medium tanks, M26, SPGs) were equipped with the 4-lb CO2 fire extinguisher -- often manufactured by Kidde. They were painted in either a medium green or red or OD.
http://i165.photobucket.com/albums/u58/HinniB747/FE.jpg
Here's one of the smaller, brass ones; http://jeepdraw.com/images/jeepdraw/Restoration2/Fire_Extinguisher_Bracket.jpg