A Patek Philippe stainless steel watch is highly coveted by collectors. One of the rarest and most expensive Patek Philippe is Reference 1518 in 2016, which fetched a cool US$11 million, making it the most expensive wristwatch ever sold at that time. 

So it's interesting that Patek Philippe, one of the last family-owned Swiss manufactures, has chosen to craft the new Ref. 6007A-001 Calatrava in stainless steel - and one that is also produced in a limited number. But the reason behind its existence is to celebrate the completion of Patek Philippe's new 10-storey production building with a space expansive enough to gather all of its ateliers under one roof. Built at a cost of 600 million Swiss franc, it houses everything from the production of movement parts to the the rare handcrafts department to facilitate a smoother production process and prepare the manufacture for its growth in the next three decades at least.

See also: Rolex & Patek Philippe Exit Baselworld