Peter, yours is from about 1919 from boxed sets I have seen.
These cases were indeed used in the teens as you are hearing on many of the Hamilton models, some were triple hinge and some even made in 14 K Solid Gold.
Hamilton made about 4 early factory cases. The one you are showing is the type I believe were used on the 956. Most all correct 956's that I have seen including boxed examples come in this case.
The 994 were factory cased in the 14K and non gold cases.
Hope this information is of help to those who might be unfamiliar with these interesting cases.
When opening this case, the bezel rocks forward, being hinged at the 6:00 position. For movement access you then carefully insert your thumbnail or sharp case-knife on the edge of the movement ring in a cut-out located by the 3:00 position. The ring which holds the movement swings to the left being hinged at the 9:00 position.
Below Hamilton factory case number 10618872 with "Hamilton Watch Co., Lancaster, Pa." along with the Hamilton crest and "Guaranteed 25 Years" markings.
Here is one opened up to show how these work...
Posts: 10553 | Location: Northeastern Ohio in the USA | Registered: November 19, 2002
The clamshells were used mainly on the lesser grades and not usually the high grades, but they are still neat cases and being they are old cases, finding any of them in good or better condition is a hard thing to do.
Also, Lindell, yours probably dates to 1919 as well, although I do have a couple very close in serial number to yours that are late 1919 or early 1920 and one, only a few thousand numbers different from your case is engraved 10/7/20 which is probably/obviously when it was sold by the jeweler. The clams are neat in design and I wish more were still with us and not worn away. Happy "early Hamilton case" Hunting!
Ethan, It appears your watch is original. Or I should say movement original to the case, movement dating to a finishing date of 1911 by the Gelson list and the case is a dead on match by serial number of the same year when compared to boxed sets I have seen.
