Off topic but kind of worth knowing. Results from search within this thread don't obey the spoiler tag (or any other BB code really).
Interestingly enough (this was mentioned a few pages back) there is Meyneth's Monado (or Meyneth Modado as its translated) in-game. The Japanese data page (this site) says "Battle for the event" in the comments field (for unused weapons it has more straightforward comments) which I guess means it was equipped for the 7th vs. Zanza fight or planned to be (weapon I had on 7th at the time seemed to have its gems removed after the battle...but I was not paying enough attention to the weapon model to check if I was using a different weapon) or used as a cutscene model. Looks like this Its attack is 340-400 (average 375), fixed gems (I think its unbeatable VI, Damage heal VI and Arts Heal VI; might only be unbeatable VI only in EU version). Given I was not getting Arts heal in that fight it might not have been equipped at all but the gem configuration and Zanza being a rather low level (masked behind the ??) point towards a battle you can't lose (given its at the start of that chapter, it would be bad if players could stuck there, then again maybe nobody ever lost).
Pretty sure you can check on it since I think you get a Party Change notification prior to that particular fight, so you can go into the Menu and look at it, but you can't change it out. The weapon's gem abilities sound about right from what I remember. Too bad you don't get it outside of that particular fight.