Certainly it is true that the World Time Watches and the Ten Day Watches of Patek Philippe are simple watches to make. After all they made 3,000 ten day watches, and probably could have made even more of them. I would guess they have made double to triple the amount in all the world time watches since 2000. Most likely anything 5970 and above with Patek Philippe is much more dificult to make, as I have stated in the past.