The frame is bronzed which is a process in which they use a torch to heat/burn the frame. Sorry I am not a gunsmith and the guy who did the work has moved away and I have been unable to contact him to get an explanation. The gun was done for a convention in which the smith had various examples of the kind of work he has done. For you 1911 fans, he now builds custom guns for Republic Forge in Texas.
Bobby there is a similar seracoat finish but this one is not that. See post below.