Bill Tindall, E.Tn.
Chromium oxide is harder than silica so I can see that before the development of synthetic abrasives it would be a good choice, perhaps because of its hardness or because it was available as a fine particle.

By my recollection it was not used for polishing metal specimens when I used the polishing lab for polishing metal surfaces. We used a fine particle alumina slurry for the last step or two.

Today we have available alumina in graded fine particles, I suppose as fine as chromium oxide. Other than it comes in a handy stick form, is there any reason to prefer it to aluminum oxide of similar particle size on a leather strop?