perhaps we use a different terminology for something very similar.
a mac address is a unique identifier attached to most network adaptors
wiki
In computer networking a Media Access Control address (MAC address) is a unique identifier attached to most network adapters (NICs). It is a number that acts like a name for a particular network adapter, so, for example, the network cards (or built-in network adapters) in two different computers will have different names, or MAC addresses, as would an Ethernet adapter and a wireless adapter in the same computer, and as would multiple network cards in a router.
perhaps your mac code is spawned in conjunction from a mac address as well as the isps data to formulate a unique code for that machine.
wiki
In the UK a Migration Authorisation Code (MAC) is a unique identifier used by broadband consumers when they wish to switch broadband service provider. The code was introduced by Ofcom and BT as a voluntary code of practice and is now standard practice for most service providers.
It appears its only a uk specific code. interesting.