Antique Graniteware Cowboy Coffee Cup Brown and White

True graniteware is supposed to be the speckled pattern but everyone calls all the various swirl patterns graniteware. Not really sure about all that although having a few tons of graniteware/enamelware. Generally enamelware is for the solid colored pieces. Actually it is all enamelware which pretty much is glass coated metal. As it is glass it is very fragile so every time it gets drops, gets dinged and so on the enamel coating breaks off and oxidation appears aka rust. The advantage to enamelware is that it is light and easy to clean. As t is light and easy to clean this is something a cowboy would carry although others would use it too. It was also used for chuckwagons.
This is a rather large cup as it is 4" wide, running around after cows would require a large coffee cup. It may be a bit before one gets a refill. Have a coffee pot of similar vintage in the last photo. Graniteware starts in 1885, the swirl patterns lose favor by the 1920s thus this cup is most likely over 100 years old.