In this extended abstract, the Open Preservation Foundation’s Archives Interest Group reports on our ongoing investigation of significant properties of spreadsheets. Using the InSPECT methodology for investigating significant properties of electronic content, our goal is to get hands-on experience in investigating the significant properties of deposited spreadsheets by adding a Spreadsheet Testing Report to the InSPECT Testing Reports lore. An additional result of the AIG investigation is a Spreadsheet Complexity Analyser tool that extracts spreadsheet- specific properties and can be used to calculate the complexity of a spreadsheet based on the values of those properties.