82 catalogued fragments of the Antikythera Mechanism are kept at the National Archaeological Museum in Athens, Greece. The seven biggest fragments are designed by letters from A to G,while the small fragments are numbered from 1 to 75. The cataloguing, description and numbering scheme was done by Mary Zafeiropoulou in 2005.
The fragments are described as “A-1” for “Fragment A, Side 1”. For the major fragments (A, B, C) this corresponds with Rediadis - Svoronos 1903 and Price’s “A1” etc. (see Price 1974), where “1” refers to one face and “2” to the other. We do not in general yet know which face was facing “outside” and which “inside” the device. Indeed some of the fragments may have been entirely internal and some on the inside face of the plates that were closing the Mechanism.