The Mercury was displayed for the first time in 2742. This 'Mech debuted as a replacement for the aging Wasps and Stingers in use by the SLDF. The Mercury is built around its LTV 160 engine and the MASC system that acts on the 'Mech like a supercharger. The Mercury also features an advancement in weapons installation using a modular replacement system to allow easier repairs to the 'Mech. This modular repair system fell into dissuse and stagnated in the Inner Sphere and the full potential of modular weapons would not be realized until the appearance of the Clans and their OmniMechs.
The Mercury carries an assortment of energy weapons. The primary weapons are the two Martell Medium Lasers which are supported by two Hessen Small Lasers. This type of arrangement is typical of lighter 'Mechs that do not have the space to carry large weapons due to their weight.
- MCY-98 - This variant of the Mercury is the downgraded version introduced in Technical Readout 3025 Revised. This variant also caries the same armament of two Medium Lasers and two Small Lasers and retains the LTV 160 Engine. The primary changes in the 'Mech are the armor, which is downgraded from Ferro-Fibrous to standard armor, and the MASC system, which has been removed to allow for the armor to be one ton heavier, lowering its maximum speed to 129.6kph and slightly increasing the overall armor protection.
- MCY-97 - This variant of the Mercury was created by the ComGuards for recon duties. The armor, engine and MASC system are kept and one Medium Laser and one Small Laser have been dropped in favor of a Beagle Active Probe giving the MCY-97 Mercury superior enemy detecton capabilities at the cost of half of its firepower.
- MCY-102 - The MCY-102 is the most recent update to the Mercury. This variant retains the engine, MASC, and armor of the MCY-99 but carries 2 major modifications the first is the rebuilding of the chassis using Endo Steel. The change in the chassis construction allows for, with the removal of one of each Small and Medium Laser, the use of a Improved C3 computer making it capable of operating with 5 other 'Mechs in a C3i unit.