Another of A. Lange & Söhne's über-movement watches is the Double Split. The depth of this calibre is extraordinary, and can best be appreciated in the video link below. I was so infatuated by the back for so long that it took me a while to actually notice it is incredibly beautiful from the front too.
YouTube video of the watch in motion, highlighting the incredible depth to this movement:
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Watch Collecting Lifestyle puts a macro lens to good use