It would be an instance variable at the family level, also called a family instance variable, so on the family object Towers you can add an instance variable 'stamped' for example. Then in a general event (order doesn't matter), you can add 'on mouse click release' and 'Towers.stamped=0', set Towers.stamped to 1 (0 is default).
Another way to do the same functionality without using mouse click is to have an event 'Family Towers on created' - wait 0.1 seconds, set Towers.stamped to 1.
Then returning to your original event for rotating, you add a condition 'Towers.stamped=1', means it won't be rotated at the same time it is created but on second click it is possible. You can then remove the black square from the family also.