Who makes the original Porsche water pumps?

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We know which companies supply oem wipers, wheels, radios, engine mgmt systems, ACs, and pretty much everything else on these cars. Given its critical role and the highly rumored superiority of oem over aftermarket waterpumps, I would like to know just who the heck the oem suppliers are. Oem suppliers and even specs will often change over time, confusing matters more. Only if we know the actual manufacturers can we hope to tease out myth from reality and have a meaningful discussion about the lifespan of this part.
Saying "just pay the dealer and don't worry about it" is counter to the whole notion of having forums such as this, whose role is to promote the free exchange of information for the education and benefit of the entire community.
If you don't have knowledge to share but still feel the need to get your voice heard, at least try not to discount a valid question for the lack of something useful to communicate. These kind of questions give value to the forum...