I am doubting the legitimacy of it altogether. The hands appear to be aftermarket Rolex style hands (new too) and the dial isn't anything I or a few other 844/1000 collectors have ever seen before. I would return it and hold out for a legitimate Monnin if that is what you are after.

Also, the listing description doesn't instill any confidence that this is legit and anything other than a jumbo case (not necessarily Heuer either) with a refinished dial, a common FE 4611a movement and some ebay Rollie hands.