The TAG Heuer Calibre 6 is based on the ETA 2895-2 automatic movement. TAG also uses a high grade variation of the 2895 which is COSC certified. Most, but not all of the Caliber 6 movements feature Côtes de Genève decorating on the rotor, which is also engraved with TAG Heuer / Calibre 6 / Swiss Made.
From Tag Heuer:
All TAG Heuer automatic movements are made in Switzerland and must meet extremely strict criteria for precision before they make it onto your wrist. Their high frequency ensures excellent mechanical precision. A number of TAG Heuer automatic movements are awarded an Official Swiss Chronometer Control (C.O.S.C.) Certificate, the ultimate recognition of precision and reliability.