Geoscientists undertaking mineral exploration sometimes are provided with historic geological and geochemical information about a prospective mineral deposit that they would like to use in a modern mineral resource assessment. Unfortunately, these historic datasets may lack critical information describing the quality of the data, such as duplicate samples, that are required under today’s disclosure regulations. As a result, geoscientists sometimes need to generate such data quality information after the fact (a posteriori). This contribution describes how duplicate samples can be obtained from historic drill-core to provide an unbiased assessment of grade and measurement error, as well as ensuring equivalent geostatistical ‘support’ in all samples, while at the same time retaining at least one quarter of the drill-core in archive for all sample intervals. It also describes an alternative method that can be applied to unsampled drill-core (a priori) to acquire unbiased grade and measurement error estimates, ensure equal sample support, while at the same time retaining half of the drill-core in archive.