That was one of the questions I put to the museum "Are you sure that the 3000 pieces doesnt relate to the Swiss made examples?" The answer was no, that was the total number earmarked for the US market, according to their production records.Can't doubt the source, only the information itself. I know it's all we have. As ulackfocus suggests, maybe this figure is just for the steel cased versions assembled in Switzerland and/or the two adjustment versions, which seem to be much less common than their unadjusted brothers.
As I say, hopefully, somehow, some new info may emerge over time that clarifies this question. I dont think we should hold our breath though