Here's a Dueber Watch Case Co., 3-Hinge, Open Face Case. It's Gold Filled w/ a 25 yr. Guarantee, as well as having it's Original [matching] Case Paper.  

Front View. This is a Late Style Case {1900 & Later}. It's thinner & has a smaller Bow & Winding Ball than the earlier Cases.

Case Back. Engine Turned, w/ Hand Engraved Shield Design. Case has no Monogram & hasn't been Polished. 

With Front Lid Open. The 3-Hinge Design makes setting the Watch a lot easier & the Dust Cover adds protection for the Movement.

Back Lid Open, Showing the Dust Cover & the Case Label.

Original Case Paper, w/ Numbers that match the one's stamped on the Case {in this instance No. 6098353}. It also shows it's 14 Karat Gold Filled & Guarantee not to Wear for 25 Years. 

Side View, showing the Coin Edge Design & the thickness of the Crystal. An Excellent Case for one of my 1900 & later 18 size, Model 3's.  { The 1908, 21 Jewel, DR, John C. Dueber is the best movement for this Case. }. The Crystal has a tendency to pop out of the bezel, so I'll take it over to Jimmy @ Anderson's & have him apply a bit of  ultra-violet glue.