Developed by the Terran Hegemony in the 25th century, the Mackie was the first true BattleMech. Based on advanced technology that the Hegemony Armed Forces (HAF) had been developing for decades under Director-General Jacob Cameron, the Mackie was the ultimate manifestation of Hegemony military might. The Mackie’s first combat trial was on February 5, 2439, outside of Yakima, Terra. The pilot, Colonel Charles Kincaid, utterly obliterated his test targets, four remote-control Merkava heavy tanks.
When the Mackie was first built, it epitomized the Terran Hegemony's technological advantage over the great houses. It was the pinnacle of military technology until 2455, when the plans were stolen by agents of the Lyran Commonwealth. Still, the Mackie had such symbolic importance to the Terran Hegemony that it remained in production until the start of the Amaris Civil War, although it has not been built since then. [Source: sarna]
You can download the papercraft model here: Classic BattleTech - Mackie Free Mech Paper Model Download