The Iron Machine Soldier was a weapon that was created by the Golden Order and the scientist Edgar Bowman, using stolen parts from a damaged Frame Gear, and reverse-engineering the technology. However, in comparison to even the most basic Frame Gear, the Iron Machine Soldier is inferior in performance, function and overall design. In the English Light Novel they are referred to as the Steel Battalion. 
After the first introduction of the Frame Gear, the Yulong Remnants immediately saw its potential as a weapon of war, and made several attempts to steal the technology . All of these attempts ended in dismal failure. It wasn't until after the second Phrase Invasion, that inferior copies of the Frame Gear were created. This was accomplished by having the Golden Order steal parts from a damaged Frame Gear, and having the escaped criminal, Edgar Bowman, reverse-engineer the inner workings, thus creating the Iron Machine Soldier.
The Iron Machine Solders were then mass-produced and used during the Yulong Civil War where the fifth false emperor made a bid for power.. Due to the overwhelming power of these inferior machines, the false emperor easily slaughtered all other contenders. This caught the attention of Touya Mochizuki, who would later investigate the appearance of these crude imitations of the Frame Gear. He would later learn that the Golden Order planned to invade the Magic Kingdom of Felsen with these weapons. 
The Yulong Civil War would eventually lead to the utter destruction of the country as the Iron Machine Soldiers and Wood Golem army proved to be no match against Frame Gears. The government of Yulong collapsed entirely and the facilities used to mass-produce the Iron Machine Soldiers were destroyed. 
However, the Steel Battalion would make a return appearance some time later in the Kingdom of Horn.  The remnants of Yulong's spy faction, the Qulau, had joined forces with the remaining members of the Golden Order and had been quietly pushing Horn toward civil war by supplying both sides with improved Iron Machine Soldiers. However, this plan would end in failure with the interference of Touya once again.
The Iron Machine Soldier was described to be shorter than a basic Frame Gear, with a squat, bulky body and lack of a head unit. It had long arms, short legs, and a wide body. It was constructed from far lesser materials, (most likely from iron or crude steel), and had simplistic controls. Though it could be piloted, few mechs had pilots with sufficient magical power and the majority were remotely controlled. Touya likened the controls for the Iron Machine Soldier to an old school arcade game with the A button for attacking and the B button for defending based on what he witnessed during his brief fight with one in the former Heavenly Yulong Empire.
The Iron Machine Soldier could be armed with melee weapons such as lances or swords, but it lacked in long-ranged weaponry. Its movements are crude, clunky and simplistic, making it an easy opponent against a Frame Gear. In fact, during the Yulong Civil War, just a handful of Frame Gears were able to defeat an army of Iron Machine Soldiers with little effort. Overall, the only use for the Iron Machine Soldiers were as cannon fodder against the Frame Gears as shown when Touya used some of them when testing Leen's and Linze's personal Frame Gears (Grimgerde and Helmwige)
After the army was destroyed and their manufacturing facility was shut down, Regina Babylon would go on to say that she was amazed at how clumsily the Golden Order had bastardized her design.  At present, the few remaining Iron Machine Soldiers are now just wreckage and are used for Frame Gear target practice.
The improved version of the Iron Machine Soldier found in Horn had incorporated Gollem technology and are fully automated. As commented by Yae as she fought them in her personal Frame Gear, they were somewhat sturdier than their predecessors. However, they still couldn't compare to Frame Gears and were easily destroyed.