A while ago we solved the problem of the enlisted rank insignia of the UNSC Marine Corps via careful observation of available images and cross-referencing it with known facts. We decided that UNSC Marine insignia is exactly the same as U.S Marine insignia, and I'm happy to see that the insigne have been added to the corresponding rank articles. (although we have had to assume that the insignia for the UNSC's SgtMajMC is exactly the same as the U.S counterpart as well, down to the Eagle, Globe and Anchor emblem) See my blog here.
However, I have observed in recent weeks that U.S Army rank insignia has been added to UNSC Army enlisted rank articles. This should stop at once: We'd never been informed what UNSC Army enlisted insignia might look like, so we had no grounds for putting the images up, and why on Earth would the UNSC Army use the Great Seal of the United States it its insingia for the Sergeant Major of the Army? Furthermore, recent images from Halo: Reach have proved that UNSC Army enlisted insignia is more akin to the British Army system than the U.S Army. Consider the image of the two Army personnel below on the left.
On their chestplates you can clearly see two downward-pointing chevrons, the insignia of a British Army Corporal. "But this is concept art!" you scream. "The final version may well be very different!" Well, would you please observe the image below on the right.
It has to be viewed in full resolution, and is very difficult to see, but to the left (your left) of his Combat Knife, just above the rifle in the centre of his chest, you can see a black mark pointing up to his shoulder.
I know, I'm reaching, but we followed concept art to work out Marine rank insignia as well, and it's also going to be difficult to reconcile U.S Army-based UNSC Army ranks with British-derived insignia, but since we know this now, I suggest to you that we brashly assume that all UNSC Army enlisted insignia is based on the British Army pattern, just as we did with UNSC Marine enlisted insignia.
Your opinions and input, please.