These mainly consist of inspection reports from each climate station with details of instruments used and a diagrammatic representation of the observation site layout. They can also include maps of the exact station location, various administrative correspondences, and even occasional photographs. These files can be used if a station ever moved geographical position or changed its name at some time in its history.
They can also be helpful in explaining a set of anomalous data figures in our records, for example perhaps there was a problem with the site or the instrumentation type was changed at some point in its history, which would have been recorded in the official inspection report. So they can prove invaluable when determining the accuracy and validity of the data produced at a particular site.