Halo: Combat Evolved
Stamped onto Halo: Combat Evolved's M6D Pistol are two Japanese or Chinese characters: The Kanji and seven characters that can be seen only with the aid of a scoped weapon, such as the Sniper Rifle.
The second Kanji is found on the bottom of the magazine floor plate, and is the character 力, chikara(jp) or li (ch). Meaning "strength" or "power", it appears to reference to how powerful of a weapon the M6D is.
In Halo 3, the M6G Magnum Sidearm features a Korean Hangul rather than a Japanese kanji. It is found on the bottom of the magazine and it reads 일곱 (il-gohb) , when reflected. It translates to number 7.
Halo 3: ODST
Halo Living Monument
A rear view of the M6G. Note the Korean Hangul.
A closeup on the laser module of the M6C/SOCOM. Note the Korean stamped characters on the side.
七 clearly visible on an officer's sidearm in the Halo Living Monument trailer.