The j's are the year code - which I am guessing is about 1882 - there doesn't appear to be adefinitive guide. E.Cotterill & co ran from 1846 to about 1930.
Could you tell me if the key is about 3.5" long or more like 5.5", or maybe even smaller, I'm guessing 3.5".
Most of E.Cotterill & co lock designs were used in safes and heavy duty padlocks. The locks are worth a lot of money (minimum $1000) in the collectors market
In a time of universal deceit - telling the truth is a revolutionary act. George Orwell
When the debate is lost, slander becomes the tool of the loser. Socrates