B777 Captain reports discovering during preflight that the FMC database for another aircraft type had been loaded in his FMC. Maintenance was consulted and the correct database loaded.

Narrative

During the cockpit set-up for our flight at the gate; upon checking the Ident page of the FMC; I noticed the database was current for date; but was an incorrect database for the B-777; showing as a AB1 instead of the correct AB2. I looked in the manual to confirm the database was incorrect but could not find text that specifically identifies the database should be AB2; only a display text of the Ident page with AB2 on it; in a timely manner. After a while; I could not find specific language in the manual normals section but found it in another section at the bottom of the page; with a revision bar next to that item on the page. We called Maintenance to resolve the incorrect database issue. Local Maintenance was unsure as to the Maintenance Manual requirement of the specific database; so I called Maintenance Control who confirmed the database should have been loaded as AB2. While on the phone with Maintenance Control; we reviewed the history; since the aircraft had just recently returned to service from a 'C' check. The incorrect database AB1 was loaded at the time of the 'C' check and Maintenance Control confirmed it needed to be changed to the correct AB2 database. The AB1 database was for a different aircraft. Local Maintenance loaded the correct database and we departed. The aircraft routing after the 'C' check was a ferry flight then a revenue trip to where we picked it up. Another note for taxonomy purposes; the aircraft came out of a 'C' check; but had numerous write ups on the previous 2 legs of pack issues; and the left pack was deferred on our leg with the resultant lower altitude filed. This flight was to be the required verification leg prior to ETOPS. As you could tell; we could not confirm the normal ops to send the satisfactory verification leg as complete.