As stated in my earlier post (ie.2499 has a lower total production). However, I always suspected that the 5970 was a transitional model, until Patek had their in-house movement ready for launch.
So, given the tremendous costs associated with bringing a new Patek model to market, especially a grand complication (tooling and advertising costs, R&D etc), this production run from approx. 2004 to 2008 (???) is very, very short indeed.