I have the tools needed to "jewel" metal. I get a few customers every year that want jewelling done to ceretain parts of their firearms and it does, IMO, add some pizzazz if done correctly to the right parts. Another place many like to have jewelled is the bolts of rifles. The jewelling gives oil someplace to adhere to thus helping preserve the metaland some think it helps slick up the bolt.
As Dan said, it is very easy to polish it off if you don't like the looks, fine emery paper on a known flat surface (granite surface plate or a piece of glass, nice easy movement, no need to press hard, and it will be off in a matter of minutes.