No. A gold challenge coin is gold plating over a base metal such as zinc alloy, brass, iron or copper. It is not solid gold, and no standard custom challenge coin from any manufacturer is.
That’s a manufacturing reality rather than a compromise. Solid gold at coin weight would cost thousands of dollars per piece, which is why challenge coins have always been plated. It’s also why they can be handed out freely, carried in a pocket and passed around at a coin check without anyone worrying about the value.
The plating is a real metal layer applied electrochemically to the finished coin, so the color and shine come from actual gold. It simply sits as a thin surface layer over the struck or cast base underneath.
The same applies to silver, copper, nickel and black nickel plating, and to the antique finishes.
What plating means for you in practice: it wears at contact points over years of pocket carry, particularly on raised surfaces and edges. Many people consider that patina part of the appeal on a carried coin. A coin kept in a case or a display holder will look the same in a decade as it does today.
Browse finished coins in the gallery to compare plated finishes, or read what actually makes a coin valuable.