We’ve come a long way from using statues of Roland in town squares to determine the price we get for our lumber, but we still need a standard somewhere to keep us honest, or indeed to enable us to make decisions at all. In New Zealand, the Measurement Standards Laboratory realises and disseminates the international system of units to allow freedom to trade, innovate and to protect wellbeing. To be sure that we’re doing things right (for example that the second in NZ is no longer or shorter than in Canada), we regularly compare our results with those of similar institutes internationally to search for systematic errors that may have snuck into our instruments. I will talk about traceability and the evaluation of uncertainty of measurement as well as the analysis of results obtained from measurement comparisons and describe some of the interesting questions we are cracking our heads over.