The first Waterbury Company was organized in 1814, and it may be the one that marked the back of it's buttons. Another firm of the same name was formed by Scovills in 1849 for the production of "German Silver Goods” This button is extremely rare.
It is an authentic button.
It was made by Scovill.
These buttons were made from 1836 to 1902 in different variations.
Lots of info on Scovill on the web.
Google is your friend.
Search : Scovill Waterbury.