Here's my example to show you what you can do. I guess you're right, it's coated for preservation. I've tried my own take on it.
I gave the Principled BSDF a slight (estimated) Roughness of 0.2 for the original underlying paint. Since the rim seems to be more of a golden color, I plugged a black and white ring texture into the Metallic socket, so that everything is black (or 0) except for the rim which is white (or 1) and therefor metallic.
To recreate the protective coating (which looks quite shiny), I set Clearcoat to 1 and Clearcoat Roughness to a very low 0.01 (you might even go down to 0).
Since the scratches in the surface come from the broken paint, I thought it would be best to have them in the original surface Normal as well as in the Clearcoat Normal. I've taken some sort of scratch texture, plugged it into the Height socket of a Bump node and this into both normal inputs.
For the lighting I took four planes with a strong Emission shader to act as lamps and positioned them so that they can be seen in the reflection on the shield. The slight blue reflection comes from an Environment Texture which I used for the world.
My result:
My node setup:
The metallic map:
