I hope the images are sufficient to help date the piece and tell me if it is Britiannia metal, plate or silver.
It does not matter what it is, it has given me pleasure all these years.
LizP
Your hot water pot is almost certainly electroplated - it is certainly not silver. It is not going to be possible to date it accurately but the style looks very late 19th century.
It cleans like silver because the electroplating process has deposited an extremely thin layer of pure silver on the surface of the base-metal body. When cleaning you should be very careful not to remove this surface silver.