Old soviet circuit breakers (15 pieces) and sockets (6 pieces) with a touch of dirt and in the finish version.

I draw attention to the number of polygons and vertices !!!
Polys: 510756 (whole scene) 12000 (average for one switch or socket)
Verts: 521404 (whole scene)

It is very important when loading texture maps to save the set values for the gamma (Automatic or Override 1.0). To load Diffuse and Reflection maps set to Automatic. Override 1.0 is installed to download Reflection Glossiness Fresnel IOR and Normal map maps.

Who works in the V-Ray version lower than 3.1 be careful in the materials in the BRDF section there is Microfaset GTR (GGX) if your version is older than 3.1 then the BRDF field will be empty. Choose Blinn Phong or Ward – which is preferable for you.

For Corona render it is recommended to install a version of at least 1.5 since the glossiness of materials is configured with PBR in mind.