I heartily agree with what Jan Hedlund has posted.
Breaking that little glass piece off the tube wrecks it. There is no repair, except to replace the tube.
The risk to you cannot be understated. The High Voltage stored in the tube and the FlyBack transformer and connected Big Red Wire attached to the side of the tube are the biggest threats, (even after the power has been off for months). Connecting that Voltage through your body (e.g., hand-to-hand) can stop your heart.
Also, bumping any high-vacuum tube while handling can cause the tube to implode, spraying fragments of glass everywhere. (Except that your old one no longer has a high vacuum, so it is no longer a risk from that.)