Top positive review
EDUCATION: It is NOT rust on the coarse sharpener. The bronze colour is called 'brazing'.
April 15, 2016
I am a mechanical engineer.
What many reviewers have mistaken for rust around the metal coarse sharpening side is actually an alloy used to 'braze' on the carbide insert that actually does the sharpening.
This is stated in the product description.
Look up brazing on Wikipedia.
If you look closely you'll see the bronze colour surrounds a rectangular block, which is the carbide sharpening material.
It is set in place (into a ground out section, which is why the surrounding bronze colour always fills out a circular arc) using the technique called brazing.