[Arran]

Looks a lot nicer... Good Job. Now put it the "makeshift" lathe and spin it, use a file to make the indentation mark while it is turning. Of course don't file to far in or you go through it, depending on how thick the wall is.

 What Kirk would need to do is find some way to put that groove in there with a roller, a file will likely just weaken it if not cut through, and it still won't look like the original anyhow. The only purpose for that groove to be in there is to help hold the hard rubber/Bakelite threaded insert whilst the bottom of the can is rolled over onto it. Even if it were left off the repro can would still be a huge improvement over an empty hole in the chassis.
Regards
Arran