This is an unusual item.  This hot water bottle would have been used in a horse drawn carriage or coach, for use by both the passengers, and the poor coach driver up top.  The bottle has a screw top where it can be filled with water, and two soldered hoops to the back to enable it to be worn on a strap around the neck.  The bottle is nicely convex so as to fit around a chubby cabbie's waist. 
 
Not in the most fantastic condition, and probably very unsuitable for use now. There are several leaded repairs around the rim, and the odd dinge to the brass. 
 
Dimensions: 28cm x 18cm