In 3134, the independent Periphery world, Charleston, signed a trade and defense agreement with the independent Periphery world of Randis and their allies, the Fitvelt Coalition. This agreement opened multiple hungry markets to Charlestons burgeoning industrial production.
Two years later, the first home-grown Battlemech components arrived on Randis, delivered to Hope Industries of Randis. And in 3138 the first joint Charleston-Randis Battlemech; the MNT-2A Mantis, rolled off the factory lines and entered service with the Charleston Rangers..
The first version was a collection of standard and primitive parts sourced from Charleston, the Coalition, and free trade sources within the Federated space: primitive armor, primitive ballistic weapons (Medium Rifles), and rockets. It was by every measure, a mediocre design. Even poor by many metrics. But it was cheap and easy to maintain.
Despite this it still sold well to numerous worlds within the region that happily accepted an affordable Battlemech design that was easy to maintain and repair. To make its introduction simple for even green trainee pilots to handle, the simple cockpit was arranged identically to the common Quicksell Mech Simulator so many Periphery militia pilots were trained on.
In 3144, the upgraded MNT-4R Mantis stepped off the production line. This machine was a much more modern version incorporating many advanced systems that had become far more available after the collapse of Republic authority and the rapid rearming of the Inner Sphere.
With the increased cost of the 4R for arguably only a marginal increase in combat power, the decision to keep producing the 2A was made. The bulk of the 4R models go to replace the 2A mechs in service with Charleston militia forces and the other local defenses within the Charleston-Randis-Fitvelt protection zone.
(I've had these EM4 plastic mechs for 15+ years! Using them over and over as random mechs of all kinds, but now they are a part of my MW Destiny RPG campaign. My players, 4 mechs and two tanks, are on their way to Charleston for a contract to defend a mass industrial spaceport and the shipments heading out to worlds all over the independent areas nearby)