This is a RARE find, WWI era Silver Plated Metal Hot Water Bottle . The plug on top is marked "Pat. Mar. 27, '06 & Oct. 27, '08. "Also In Russia, Australia, Austria, France, Germany, Great Britain, Japan". In the center on one side is stamped; "STAR Quality Hot Water Bottle"  Not sure, but likely a military issue  medical item during or around the time of WWI. . 

Measures 8" Diameter, 2-3/4" Thick

The threaded plug works well. Much of the plating has worn off, there is a dent and a small damage area on one side that has been repaired. See all photos for details.