3D collections are basically the same kind of collection as the regular online collections. We put this separately because they use different kind of method and sometimes they provide the 3D files that one can download and print using 3D printer.
Most 3D collections are done with the aim to use the object as a replacement of the original one, or as teaching material when the original object cannot be removed from their storage or display case. This way, visitors and scholars can examine the object without fearing of damaging the original one. The other advantage is one can examine all angles of the object when certain section cannot be seen due to object placement in the display case.
British Museum
https://sketchfab.com/britishmuseum
Minneapolis Institute of the Arts
https://sketchfab.com/artsmia
Smithsonian
https://3d.si.edu/collections
Other collections on sketchfab lab:
https://sketchfab.com/members?segment=organization%2Fmuseum&cursor=cD0yMjImbz0x
Bonus:
Radio-ontvanger NRI, type Marine B - Netherlands Institute for Sound and Vision
https://proto.virtualinteriorsproject.nl/3d/experimental-radio-prototype/
(slow upload. But it's a cool example to show what's possible in 3D model)