Hello! Here is the basic node setup I created for the gun. I got imperfections from quixel (another good free website is ambientcg for imperfections) and for the gold effect I got a noise texture and turned the strength and distance down quite a bit to make it more realistic. Then got a color ramp to edit the roughness and Mix node to mix the two imperfections.
Node setup
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Imperfections: Search Results on ambientCG