The Warmaster’s Prize Commando weapon coating is one of the many multiplayer skins you can unlock during the campaign of Halo Infinite. All of the multiplayer skins in the campaign are found by unlocking Mjolnir Armories across the map. Of course, you need to find them first. Here is where you can find the Warmaster’s Prize Commando weapon coating in Halo Infinite.
The Mjolnir Armory that you are looking for is found along the southeastern edge of the map near FOB Lima. It is also located next to one of the spires for the Sequence mission. Take a look at the map above for reference if needed. You will not be able to access this part of the map until you have completed the Pelican Down mission. You can also make the Mjolnir Armory appear on the map by capturing FOB Lima.
Head to the southeastern edge of the map. You will find the Mjolnir Armory hidden amongst the metal constructs near the edge of the land along with some other UNSC crates that are scattered about.