http://www.hamiltonwristwatch.info/Detail%20-%20Oval%20Plain%20-%20Two-tone.htm

The Oval is one of the rarest as well as one of the most desirable models that Hamilton produced. It is a classic example of the geometrically shaped watches that were commonly offered during the mid to late 1920s by Elgin, Illinois and Waltham. However, unlike other commonly shaped watches of the period, the Oval was unique in style, shape and design and, subsequently, is distinctly "Hamilton." Other geometrically shaped Hamiltons include the Cushion, Square, Barrel, Tonneau and Rectangular.

This particular Oval is a "two-tone" version - the bezel and case back are 14K white gold while the center case is 14K green gold.

Two-tone Hamiltons are extremely rare and Hamilton did not maintain production numbers for them. It is believed that they were either "special orders" or were distributed amongst several jewelers in extremely limited quantities. The two-tone Oval Engraved pictured above is one of only six known examples - one is in the Hansen Collection, one is in the Welsh Collection and another two-tone Oval Engraved resides in a prominent West Coast Collection.  Three others exist in private collections.

This model was one of six geometrically shaped wristwatches that were popular up until the late 1920's.  Hamilton's "Geometric" offerings spanned ten years - beginning in 1917 with the 0-sized Cushion and ending in 1927 with the Oval.  Included in the geometric models are the Cushion (0-sized, Cushion Round and Cushion Form Opening), the Square, Barrel, Tonneau, Rectangular, and Oval.All known Hamilton two-tone models, which include the Square Plain and Engraved, the Barrel Plain and Engraved, the Oval Plain and Engraved and the Barrel "B" Engraved were manufactured by the Fahys Watch Case Company and all are solid 14K gold.