What happened to automatic binary primary keys?

Howdy All,

I browsed Apple's documentation, Omnigroup's mailing lists, googled here
and googled there, but I can't find anything about those globally unique
binary keys that EOF used to be able to generate automatically.  I think
they were 12 bytes then jumped to 20 (or was that) 24 bytes.  They were
made up, IIRC, of an IP address, an entity name, etc etc.  

Do these still exist in WO 5.2.x?  Can someone please point me to some
documentation?   Or do they just automatically if you declare the
primary key to be NSData with external type something like Byte width of
20 etc?

Any help most appreciated as always.

Cheers,
Ashley.