This specific 3D model, "Engagement-ring 3D print model 3", is an asset made available by "Unknown author".
Can be downloaded at "Unknown platform" by following the link.
This specific 3D model is provided under the "Unknown license" framework.
STL (Stereolithography, filesize: 43.7 MB), 3DM (Rhinoceros 3D, filesize: 61.3 MB)