Apple publishes sample code demonstrating how to obtain the Ethernet address under Open Transport . The complication for this technique is that the default Ethernet address may be overridden by a resource of type 'eadr' in the System file. Networking on page 11-26 . Because it is easily possible to override the hardware address, and because Ethernet is not guaranteed to exist on any particular model, this is not a good scheme. Similar techniques can be used for a Mac OS computer with Token Ring cards or other cards, but a discussion of these cards is outside the scope of this document.
Some hard disks have serial numbers.
Apple publishes ATA demo sample code which shows how to get the serial number of an ATA or IDE drive. Only some Macintosh models have ATA or IDE drives, so this is not a good general purpose scheme. Some developers use the defect list from a SCSI drive. Devices for details of using the SCSI Manager. Only some Macintosh models have SCSI drives, so this is not a good general purpose scheme.