i understand, but there has to be a time, a year when this happened. just wondering?
It sounds like you’re making 2 assumptions I would not make. First, that “they” who made 2-piece rear thimbles joined together all switched from soft solder to hard solder in a specific time frame. Second, that we could somehow know when that was. What would be our data? There are next to zero period “how I do this” accounts by gunsmiths, and very few guns are dated and very few have 2 piece rear thimbles. So, there’s no way of knowing if there was a switch, and if so, when that happened.