Surefire 617 for Benelli fit question

[Josh-L]

New to the forum so hopefully this is the correct place to post this. I recently got a Benelli M1 Super 90 and want to put the Surefire foreend on it. It's my understanding though that there are two versions of these lights though. One is for pre s/n M104800 and the other is for later. Mine is later. I found a good deal on one but the guy doesn't know how to tell if it will fit or not. Anyone know how to tell?