Update namcos12.cpp

src/mame/namco/namcos12.cpp

@@ -3642,6 +3642,7 @@ GAME( 1999, aquarush,   0,        coh700,   lbgrande, namcos12_state,         em
 GAME( 1999, golgo13,    0,        golgo13,  golgo13,  golgo13_state,          empty_init, ROT0, "Eighting / Raizing / Namco", "Golgo 13 (Japan, GLG1/VER.A)", 0 ) /* KC054 */
 GAME( 2000, sws2000,    0,        coh700b,  namcos12, namcos12_state,         empty_init, ROT0, "Namco",           "Super World Stadium 2000 (Japan, SS01/VER.A)", MACHINE_NOT_WORKING ) /* KC055 */
 // truckk can't be a Japanese set despite the game title still being in Japanese.  The option for in-game Japanese text is disabled in this set, and it has a Parental Advisory screen usually associated with US releases
+// TKK1 is probably the Japanese release, although a TKK1 CD contains identical data to a TKK2 CD, so any difference is in the ROM data rather than the CD
 GAME( 2000, truckk,     0,        truckk,   truckk,   truckk_state,           empty_init, ROT0, "Metro / Namco",   "Truck Kyosokyoku (US?, TKK2/VER.A)", MACHINE_IMPERFECT_SOUND ) /* KC056 */
 GAME( 2000, kartduel,   0,        kartduel, kartduel, kartduel_state,         empty_init, ROT0, "Gaps / Namco",    "Kart Duel (World, KTD2/VER.A)", 0 ) /* KC057 */
 GAME( 2000, kartduelja, kartduel, kartduel, kartduel, kartduel_state,         empty_init, ROT0, "Gaps / Namco",    "Kart Duel (Japan, KTD1/VER.A)", 0 ) /* KC057 */