First gen SAA were color case hardened untill about 1935 and then went to blued with bright polished sides untill the end of production in 1940. Some produced after 1935 would still have cc-hardened hammers as old parts were used up, likewise for the prewar/postwar guns assembled after WW2. Almost all of the 2nd and 3rd gen SAA hammers have bright polished sides with the exception of some Commemoratives and a fairly recent run of Doug Turnbull guns.
It's not a real SAA, but I have one of the Doug Turnbull Cowboy Classic revolvers, with the pre-war bluing and full bone case coloring. It is truly a work of art. To me, the fully case hardened hammer makes the piece by blending the rear of the frame together.