Where it gets interesting is if you dig a little deeper into other brands. Patek Philippe's flagship watch for many years was the 5970, Patek do make in house movements, but that watch wasn't, its based on a Lemania 2310 AKA Omega Calibre 321.
Audemars Piguet's flagship sports watch, the Royal Oak Jumbo? Well it uses a Jaeger LeCoultre Calibre 2121. The cheaper 15300/15400 models have the AP in-house movement but the much more expensive 15202 still uses the JLC movement.
IWC have a few nice in-house movements but they've been paying their bills with expensive ETA powered models for ages.
Rolex is one of the strangest. Rolex SA in Geneve for 70+ years until 2004 bought all of their movements off Aegler SA in Bienne. Rolex owned shares in Aegler but didn't own the whole company, it was still a third party. In 2004 Rolex bought the remaining shares but it remained a separate company in Bienne. Rolex also bought Beyeler & Cie SA, Gay Freres SA, Rolex Industrie SA and many others who are now wholly owned subsidiaries of the group. The fact remains though, as of 2015, the manufacture in Bienne is still a separate company called Manufacture des Montres Rolex SA owned by Rolex SA:
http://www.bloomberg.com/research/stocks/private/snapshot.asp?privcapId=22863906
So is in group good enough to count as in-house? At the end of the day its not a big deal, the corporate structure and building locations matter less than the end result. Its just all grey areas upon grey areas and you can create rules and draw lines in the sand all day and not get anywhere in determining what is and what isn't.
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