How to get Ludwig's rifle?

Could you please elaborate on the steps needed to acquire Ludwig's rifle? Is this a quest in a video game, or a reference to a historical artifact? If it's a game, which game is it, and what are the prerequisites or missions that need to be completed in order to unlock the quest for Ludwig's rifle? Additionally, are there any specific items or resources that are required for the acquisition process? And lastly, is the rifle a valuable asset in the game, or does it have any unique properties or abilities?