Misriah
From Halopedia, the Halo wiki
Misriah Armories is a weapon and ballistics company based on Mars. They are most likely responsible for developing the design and ammunition for the M6 series of pistols, as well as the SRS99C-S2 AM Sniper Rifle for the UNSC. In the Art of Halo book it shows a side view of the M6C Magnum Sidearm and it has Misriah stamped on the side.
Trivia
The symbol for hand-loaded match-grade 14.5 x 114mm ammunition from Misriah is a winged hourglass headstamp flanked by double "X"s.
Misriah is also an organization in the Marathon Universe:
On January 6, 2345(Earth A.D.), at the United Earth Government Misriah food distribution center, what had begun as a commonplace food riot turned into a massacre. The UEG riot troopers who arrived at the scene had been informed that the rioters were armed. As the UEG troopers approached the scene in their Randal Hovertank, plasma fire began spraying upwards. In a flash decision, the commander of the Hovertank ordered his crew to open fire upon the crowd. It took only five seconds for over five hundred starving Martians to be incinerated.
