Though not well known, alternative trigger designs utilizing the thumb, rather than the index finger, are not as new an idea as many believe when first seeing the Iron Horse Rifle. In fact, thumb triggers date back to 1870 with the Italian Thumb Trigger 11mm Trials Rifle created by Glisenti-Pieri of Brescia.
Nearly 30 years later, it would be Winchester that filed for the first patent related to the "thumb trigger" in 1899 and 1905. Winchester introduced a rifle chambered in .22 short, lr and xlr, and they indeed marketed it as a more accurate rifle. The plinking and small game rifle was released in 1905 and hit nearly 80,000 units in sales by the year 1923. Despite steady sales, the rifle was discontinued in 1923 after William Wirt Winchester passed away, along with many other models the Winchester Co. had come out with prior.
In 2015 the founder of Iron Horse Firearms, Ryan McDonald picks up, and adds to, where Winchester left off. Arriving at the thumb-fired rifle independently, and Ryan being a former U.S. Marine, he had envisioned the use of the thumb actuated trigger on the government issued M-4 rifle. Ryan had imagined as Oliver Winchester may have, that pressing down on a trigger may lend to less windage errors, i.e., greater accuracy. Over the next few years Ryan would research into the viability of his idea and with the results he'd launch Iron Horse Firearms.