The M1917A1 liner looks to be the winner. I was focusing on Canadianicon or Britishicon items when I should have been looking south of the border. The stamps being from the United Statesicon Army Ordnance Corps explains why they look familiar but I couldn't place it, we don't have much beyond Canadian and British military items in our collection.

How the liner ended up in a Canadian shell is a bit odd. Probably someone completing a 'set' or working with surplus. The shell at least appears to have come from the local Emergency Services Department, Cold War era, which would follow the surplus possibility as I'm sure much of their stock was made up of that. It would also explain the relatively good condition of the shell and liner.

Thanks for the help and the links!