Okay, we once again have a disputed issue over game-novel inconsistencies. This has been going on for a while, and while it is a minor debate, I think I'd like to offer my opinions on it to give some suggestions.
As most of us probably know, PFC Wallace A. Jenkins was a Marine in Sgt. Johnson's squad in 2552. For those that have read Halo: Contact Harvest by Joseph Staten, it's also noticed that there's a recruit called Jenkins training for the UNSC Marine Corps in 2524-2525. Assuming he's at least 18 when he signed up, that would make him older than John-117. And a lot of people are asking, "Why is he such a low rank after 27 years of service?" It's a good question, seeing as Jenkins proved to be a distinctive soldier during the first Battle of Harvest, and it's unlikely he'd be held at the same rank during the time that a Spartan, superior he may be, would go from Petty Officer Third Class to Master Chief Petty Officer.
So here's a possibility. They could be separate characters. It's possible they're even related. The Marine Corps has a lot of soldiers sharing names. So let's assume they're not the same Jenkins. I might be wrong, and correct me if I am, but I don't recall the Contact Harvest Jenkins' first name ever mentioned. What's more, the two Marines' personalities seem to be noticibly different. I for one don't think they're the same character.
So what do you think? If there's anything you want to point out, go ahead, I'd like to hear your thoughts on this matter. While we don't have solid proof that the two Jenkins are different, we don't really have any to prove they're the same either (again, if I'm wrong, let me know), and if you have a strong argument that goes against my points, put them down below.