[Tubejunke]

That tube is not "canned" but instead has a shield over it. The tube should have simply pushed out in the direction of the pins from the shield. Sometimes the shields can be unruly and not want to let go of the tube but I have never had to "unwrap" one.

Regardless you have done no harm. Simply re-insert the tube in its socket and slide the shield down over it. If you have bent it then shape it as best you can until you can get another. As long as you get it around the tube it will do its job. It doesent have to look pretty to function....

About the spot on the tube, from what I can see the spot is shiny which is good. The spot is a coating that was put there when the tube was manufactured. I believe electrons bounce off of it or something. Someone else may want to take you down the theory road. I just know that it is no sign of age or anything bad. Now when you see a tube that this spot and other places has become milky white you are seeing a tube that lost its vacuum. These tubes are garbage...