Identify the color of the metal. Brass is a metal that is most easily identified by color and does not usually require any chemical testing.
Compare the color of the bed to other similar metals that might resemble brass. Copper is a reddish brown.
Zinc, magnesium, aluminum, tin and lead are whitish. Iron is gray or white.
Bronze is a darker brown than brass.
Chip away a small amount of the lacquer coating if the metal of the bed frame is not exposed. Brass is regularly protected with a lacquer coating to prevent corrosion.
Corroded brass turns greenish in color. However, since bronze is noncorrosive, you can safely assume that a lacquered bed is not made from bronze unless you have reason to believe otherwise.