FIGURE 1. The surviving fragments of the Antikythera Mechanism.

The 82 fragments that survive in the National Archaeological Museum in Athens are shown to scale. A key and dimensions are provided in Supplementary Note 1 ('fragments'). The major fragments A, B, C, D are across the top, starting at top left, with E, F, G immediately below them. 27 hand-cut bronze gears are in fragment A and one gear in each of fragments B, C and D. Segments of display scales are in fragments B, C, E and F. A schematic reconstruction is given in Fig. 2. It is not certain that every one of the remaining fragments (numbered 1–75) belong to the mechanism. The distinctive fragment A, which contains most of the gears, is approximately 180  150 mm in size. We have used three principal techniques to investigate the structure and inscriptions of the Antikythera Mechanism. (1) Three-dimensional X-ray microfocus computed tomography²⁴ (CT), developed by X-Tek Systems Ltd. The use of CT has been crucial in making the text legible just beneath the current surfaces. (2) Digital optical imaging to reveal faint surface detail using polynomial texture mapping (PTM)^{25, 26}, developed by Hewlett-Packard Inc. (3) Digitized high-quality conventional film photography.