It's impossible to tell between original and repro from a photo.
You need to look at the detail of the casting of the cast iron fire surround. I thought ours was original or salvage, but the man from the fireplace shop (we're having work done on it) said the quality of casting gave it away as repro. Look at how sharp the edges of the pattern are and whether you can see any little missing bits which are caused by bubbles in the metal when it was cast.