Bulova 1931 Round the World
Case dimensions: 27mm (not counting crown) by 33mm lug tip to tip.
Crystal measurements and other details to follow.
Supporting 1930 ad doesn't mention two-tone gold case, and dial configuration is different, but it's a starting point.
EDIT June 5, 2014: The 1930 Ambassador ad mentioned above has been replaced with an August 26th, 1931 ad from the Spokane Daily Chronicle.