Here is another pic

Kalanchoe x houghtonii....a hybrid between Kalanchoe daigremontiana and Kalanchoe delagoensis?

Be warned. This is an evil plant :-).

Very soon you will have hundreds of them. Every notch will produce a small plantlet, complete with roots which will drop as soon as you look at them. I swear they actually have legs as they pop up meters from the parent.

So unless you want to be overtaken by one of the most invasive plants in the universe, get out the flame thrower.

You did a good job reviving it! I'm not sure it's not plain ol' K. diagremontiana with less light than it would prefer. It can only be invasive in warmer, suitable climates. If you have freezing winters, that should kill any plants outside.