Vincent Perriard had a blank sheet of paper when they decided to re-make Concord.
So, they took a decision NOT to be derivative. Remember that Mr Perriard was at Audemars Piguet until about 1999 and was very conscious not to be accused of that.
So, they took the "best selling" Concord model at the time - Saratoga and deconstructed it's design elements. The original Saratoga was introduced in 1986 and the Mariner Sports watch earlier in 1980. The Saratoga has always had the 8 (vertical) castellations on or 'holding' the bezel.
Knowing full well the key design cues of the Royal Oak, they avoided reinterating the octagonal shape, topside bezel with 8 polygonal faux-screw slots (they're actually bolts) going vertically through and holding the RO case/sapphire glass/gaskets together, and the RO angled lugs, etc etc. Actually, the C1 has no lugs!
Anyway, the prototype C1 case shapes were "seen" by AP personnel and there was no conflict raised..............
The same cannot be said for Hublot.
Of course, there are only so many ways to make a chunky sporty watch bezel and their designers have heard it ALL before with "comparisons" to Zenith, G-Shock, Chopard St Moritz, Vacheron & Constantin Overseas Chronograph, DeWitt....just to name a few that came up in our conversation
Regards,
MTF