The story in a nutshell is that Rolex and Omega were in approximately equal competition until about 1960 when they changed their advertising from promotion of technical merit to success of Rolex owners. The book is not long on watch technical detail. It has a lot of sales and produciton information and detail aboiut the major characters.
In the case of Rolex, billions of dollars. It's one of the most recognized names in the world and by far the most widely recognized name for a watch, and is the reason why so many non-watch folk flock to its banner.
Of course, since Rolex case backs are designed to be opened and closed with a special wrench that not all watchmakers had, a lot of case backs got ruined and ended up being replaced with ones having different reference numbers.
A true Rolex would only have an aegler 15 jewel movement signed on the bridge or ratchet wheel post 1915. Other brands under W&D were sold at lowers costs compared to the rolex brand and would never feature a subpar 7 jewel movement. If its not signed rolex then its not a rolex. Even Rolex-Marconi signed movement is NOT a rolex.
Uh-oh, a web search of just "M832118" gets several results on it being a serial number that appeared repeatedly on counterfeits. I'd like to see higher resolution photos of the movement to help identify it. It appears to me to be a Swiss ETA 2836-2 movement, like roughbarked said, rather than a Rolex movement.
With four or five large, well-equipped buildings in Switzerland, Rolex is well positioned be vertically integrated and manufacture all their own parts. A possible explanation of why viral videos exist that claim important and/or luxury goods are actually made in China is presented by "The China Show" channel: (Warning - video has foul language.)