Here is an object for material previews. I call this 'material previewer'. This is specifically designed to show different material properties clearly with occluded areas, sharp edges and round surfaces.
This object was tested in Substance Designer and test bake was made with Curvature, Occlusion, World Space Normal and Position maps.
Originally modeled in Blender. Blender file has subdivision surface modifier in modifiers panel. OBJ and FBX formats have both subdivided and original meshes.
Non-overlapping UVs for baking. UVs are neatly packed.
No ngons, isolated vertices or co-planar faces. I hope you enjoy this model.