My great grandfather brought this home to my Dad during after World War 1. We recently found it again and thought it would be a fun project to figure out which bought it came from. Is it possible to figure it out and if so can one of you kind folk point us in the right direction?
Do you have any photographs of the base of the shell casing? Markings on there were used to identify the type of shell. An approximate diameter would also be useful for identifying it.
This is not directly related to the question, but do you know if that shell is live or not? Because if it is, or you are unsure, you really shouldn't be handling it. Explosives can degrade over time, which can mean that it could blow up when handled. I don't want to alarm you, but if it is a live munition, it would be best to let the authorities know.
As for your question, I'm going to assume that your great-grandfather served in the Canadian Navy from the tags you included on the pictures, so your best bets for trying to find out what ship this might've come from would be to find out what ship(s) he served on. As /u/thefourthmaninaboat mentioned, more information on the shell itself would be helpful to identify it.