That is what's known as a pair case. They're not seen all that often on American watches, but are out there(as you've observed).
At least one collector I know calls this specific design a "coffin case", probably for obvious reasons. If you look at English pair cases, the design of this is somewhat different(most English pair cases attach the crystal to the inner case) so I think that's why he differentiates these with a different term.
A forum community dedicated to watch owners and enthusiasts. Come join the discussion about watch collections, displays, watch winders, accessories, classifieds, and more! We welcome all manufacturers including Casio G-Shock, OMEGA, Rolex, Breitling, Rolex and Tudor, Seiko, Grand Seiko and others.