I wonder what type of reflection is this material more related to? Is it a combination of diffuse and ideal specular?
I think your intuition is correct, materials can have different amounts of diffuse and specular reflection and this looks like a combination. We can imagine that a more polished gold would have more specular. I think this looks like it could also be glossy specular, but the best model does seem like a combination of sorts. This page has some more relevant info and diagrams: https://www.scratchapixel.com/lessons/3d-basic-rendering/phong-shader-BRDF