Windows XP SP2b seems to have appeared in Japan. It is somehow strange because at the shops, there are boxes which are labelled SP2b but Microsoft has not make any official announcement of a SP2b.
There is no special marking for the CDROM except the box that holds it (see picture).
Windows XP Professional SP2b retails for 19210 Yen and Home Edition SP2b retails for 12780 Yen.