Not in any of my 5 Smiths- well, 6 including the OO grade- I have bot field and detail stripped the actions and ejector forearm irons on both my LC Smith doubles and my Winchester M12's- and what I have typically found on the obverse side of the lock plates, whether with bridle, tumbler and leaf springs in place, or stripped down for parts, is slightly grey looking metal surface- easily cleaned with OO steel wool and Hoppe's--

"The field is the touchstone of the man"..