Certainly is a nice one.
The 'Grey area' in the frame is quite correct. A case hardened insert for the third lock. They usually end up remaining in the frame and get reblued with it on refinished guns. A give-away if the whole job in itself isn't enough.

6 inch or 6 1/2 inch bbl? on that beauty?
I think the Target Sighted model had a very few with a 7 1/2 bbl.

Very nice find,,congrats!