>On the other hand, relationships between tables will be a lot simpler if you store the Primary key in a single field. For example, let's say you want to have a "composite" key, one part a number of the branch office, another a sequential number, generated by a function, SerialNumber(table_name).

Ah yes, I see now, to establish the foreign keys you will set indexes to both parts of your unique field. It seems an almost equivalent solution then.