This is a sparklock musket. Said weapon was developed by a civilization which had a different history of industrial development to ours. Basically in this world four hundred years earlier a continent the size of North America was unified under the rule of a single empire as it's centralized government (aided by semaphore usage) could put together a proper standing army using pike formations and (after some time refining handgonne designs) arquebusiers and use it against the various feudal kingdoms with their feudal armies. The process took more than a century to achieve, but dominance was asserted never the less. To ensure that the stability of the empire and to deal with the risk of rebellions laws were put into place laws about weapons which included an out and out ban on the private ownership of firearms. All firearms were the property of the government (specifically the army), all firearms production was handled by a small number of closely monitored government employed gunsmiths.
This policy ultimately worked, for four centuries this Empire knew peace and stability. Some efforts were made to explore the world beyond this continent but only found iron age primitives on a few distant continents which posed no long term threat. Trade thrived, the economy improved and the Empire entered a scientific and eventually industrial revolution. The army was retained but atrophied as time went on. It's role became ceremonial and to suppress the occasional riot or bandit gang that got too big for police to handle that came up once every few decades. Without any pressing external or internal threats the army stuck with it's gear and it's state controlled gunsmiths continued to make single shot matchlocks even as railways and telegraph lines connected increasingly large and industrialized cities.
Then one day things changed. In one of the provinces a group of industrialists became resentful of a battery of new labor laws which forbade the employment of anyone under 12 and limited the work week to 45 hours managed to make a deal with a romantic garrison commander and started an insurrection against the "corrupted" Imperial government, thus sparking a civil war in the Empire's western provinces that lasted four years and spurred a technological arms race as the old tactics of pike blocks, arqebusier formations supported by lancers and cavalry archers proved to be way behind the time. Among their developments was the sparklock.
Replacing the older matchlocks the sparklock uses a battery powered electrode to generate a spark to ignite it's powder and fire. This system is far more reliable than matchlocks, could work in rain and is more accurate as their is minimal delay between the pulling of the trigger and firing, though it is more expensive due to the batteries. This designed was developed by the rebels as they established their own firearms industry, but was soon replicated by the Imperial government. the insulation is made of waxed cloth reinforced paper. The design would be refined as time went on and the war progressed.