Pictured below is another Rolex wristwatch from 1915, this time with a snap front Hunting Case and if you look closely you notice it is simply a pocket-watch with  lugs soldered onto the case, along with a leather piece sewn onto the  wired lugs–very primitive and fragile by todays standards.
The  reason it had the snap front case-cover was to help protect the glass  crystal from getting cracked when a gentleman went hunting.
It  is important to note, prior to World War I, wrist watches for men did  not exist. Ladies wore watches on straps around their wrist, but men  wore their pocket watches on a chain, and they kept their pocket watches  in their vest pocket of their suit. 
During  the early twentieth century, when a man was asked what he thought about  wearing a watch on his wrist (known at the time as a wristlet) one man remarked he wouldn't be caught doing such an unrefined thing.  He said you would be as likely to catch him in a dress as you would  wearing a "wristlet."
When  you examine these first generation wristwatches, with the skinny strap,  you can kind of understand why men would have thought they were  feminine at the time.

