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The recalibration of the sunspot number series, the primary long-term recordof the solar cycle, requires the recovery of the entire collection of rawsunspot counts collected by the Zurich Observatory for the production of thisindex between 1849 and 1980. Here, we report about the major progressesaccomplished recently in the construction of this global digital sunspot numberdatabase, and we derive global statistics of all the individual observers andprofessional observatories who provided sunspot data over more than 130 years.First, we can announce the full recovery of long-lost source-data tablescovering the last 34 years between 1945 and 1979, and we describe the uniqueinformation available in those tables. We then also retrace the evolution ofthe core observing team in Zurich and of the auxiliary stations. In 1947, wefind a major disruption in the composition of both the Zurich team and theinternational network of auxiliary stations. This sharp transition is unique inthe history of the Zurich Observatory and coincides with the main scale-jumpfound in the original Zurich sunspot number series, the so-called "Waldmeier"jump. This adds key historical evidence explaining why methodological changesintroduced progressively in the early $20^{th}$ century could play a roleprecisely at that time. We conclude on the remaining steps needed to fullycomplete this new sunspot data resource.

Reconstruction of the Sunspot Number Source Database and the 1947 Zurich Discontinuity