The King Cobra was never made w/nickle finish, Colt mfg. stoped making the nickle finish in 1984-1985, starting in 1985 the stainless replaced the nickel in all the revolver line up. The King Cobra was first made in 1986 and they were available in brushed stainless, bright stainless or royal blue finish.
I've personnaly owned three S&W 586/686 and four KC in all finishes available. Now, I now only have one of them, I kept the Colt King Cobra in Bright Stainless. This is by far the only .357 magnum revolver that comes close to my beloved Colt Python in term of accuracy, trigger and overall fit and finish.
S&W 686's are very good revolvers dont get me wrong, but it's not in the same league as a Colt King Cobra.
My Bright Stainless KC is now for sale, I'll only keep my Python as I shoot mostly my service pistol in 9mm, and will use the Python for some bulleye matches once or twice a year with my partner. He will not see a lot of action, it's a safe queen and will stay that way.