Have to agree with the above comments. It is best to leave it dark; many collectors feel the darker the better. I have some rifles with so much crud on the brass that it obscures the engraving beneath. And, I intend to leave things that way. Attic/closet rifles in 'as found' condition tend to bring more money on a sale than do the shiny cleaned guns. I will buy a shiny rifle only if I feel that it can be crudded up again, and made to look as it should for its scores of years of use and then sitting around. So, your gun, your choice! Just my $.02.
Dick