Someone did have talent in making that as mentioned. I think he might have been looking for a better mouse trap.........but some of these mainsprings have lasted over a hundred years.
I agree with Tom, anyone that can make that could have made a regular mainspring. The one that would be the hardest would be the bar action mainspring.
Chris you bring up a good point. The bridle looks like it encapsulates everything. I wonder if the tension from the spring on the sear launches it forward. It being so low, would it have much tension on the hammer? I hope that if someone on here buys it, they will share how it works.