Update, 3/10/2015: Bernhard G. has created the following album of pictures (LINK HERE) comparing one of these darker hooks to another one of his own. He shows weight as well as measurements for comparison.
Update, 2/25/2015 10:00pm EST: I've now received numerous emails regarding these hooks from SPAS 12 owners here in the United States. I have spoken with both the buyer and seller at length, as well as a technician at Benelli in Italy who is familiar with the SPAS, as well as several trusted sources here in the US and have come up with the following information, please be advised before reading that I am only going to put the facts given by those I've spoken with and allow you to draw your own conclusions.
-I contacted the seller, and he immediately obliged my request to send some more photographs (seen here) of the hooks he received from a contact of his in Italy who he believes to be reputable and has gotten SPAS parts from in the past. He has noted that these hooks are parkerized black, like the barrel, not the phosphate gray/green in his auction.
-The buyer provided two videos (one, and two) depicting him with gun oil on his hands, rubbing the hook, and showing residue left on his hands.
-The seller has informed me that he has also seen the video and believes it is the protective oil coming off the hooks.
-After seeing the buyers demonstration, the technician at Benelli in Italy declared that this is not in line with the behavior of exposing any parkerized metal to oil, and he believes it is paint. He also still maintains that the pin weld is inaccurate as well as he believes the cap has a grain to it that is not in line with the factory pieces he's familiar with.
-I showed the video to a professional firearm refinishing shop here in the US to double-check and was told, "The finish used on that hook would not be parkerizing. Parkerizing chemically etches the surface of the metal."
-It was explained to me by both Benelli USA and the owner of what remains of American Arms SPAS 12 inventories that it would be difficult to discover exactly what Franchi's production finishes were like towards the end of production, as in the United States we only could import the SPAS until 1994.
-(2/26/2015) From the seller: "I will however confirm the finish is NOT paint. If it wer
e then it could be scratched off. Also the cellulose thinners would have stripped this in seconds."
I received an email this morning from a SPAS 12 owner who believes he may have been taken advantage of, and after bouncing the pictures off of a few trusted folks and doing a little Internet digging we think these hooks have a chance at being of questionable origin.
The person who has contacted me said that as soon as he put gun oil on it, the finish began to rub off on his hands. This person then got in touch with an employee at Benelli in Italy who gave the hook an inspection and said that the "F" marked cap seemed to have a different grain to it than the original as well (possibly indicating a casting). His contact at Benelli also seemed to think the finish might be spray paint. Also just looking at the pictures, the bends seem slightly off, most notably the final tip arcing back towards the main stem of the hook.
The real difference seems to be the welded-in pin showing through the rear of the hook. The factory pieces all seemto be flush ground.
The gallery below shows the hook in question. I'd invite you folks with hooks to compare yours to the ones in the picture and share your thoughts.