An examination of tool marks and other evidence of manufacturing techniques on two astrolabes of identical pattern made by Hartman (also spelled Hartmann) of Nuremberg in 1537 shows that all of the parts have been laid out with scribers and filed to final dimensions. All parts except the rings of the maters, which are castings, are made of sheet brass. The only machine tool employed was a small lathe with longitudinal feed, which was used to turn the diameters of the pins. Corresponding dimensions of the two astrolabes differ by less than 0.2 mm on average, but parts are not interchangeable between the instruments. There is evidence that this pattern of astrolabe was made in batches with division of labour in Hartman's shop. This paper is an introductory study intended to show methods of examination that reveal manufacturing techniques.