I think I've found my answer.
Certified Zombie Hunter
By the way, an adult asking a teen about something does not always get an honest answer.
Not that I don't trust my grandson, I just wanted an independent review of what the symbol might be.
Just in case it was something his mother should be concerned about.
 Al-Bundy_59
                                                
                                                Level 6
                                                Dec 28, 2018
                                            
                                                
                                                    Al-Bundy_59
                                                
                                                Level 6
                                                Dec 28, 2018                                            
                                        Well it’s either to not confuse the letter z with the number 7 or he’s a member of the polish secret police.
But seriously if he keeps it there or starts writing it on multiple personal items then get with the school and see if it’s a marking for a certain group or wannabe gang.
 48thRonin
                                                
                                                Level 8
                                                Dec 28, 2018
                                            
                                                
                                                    48thRonin
                                                
                                                Level 8
                                                Dec 28, 2018                                            
                                        It's a 'Z', with a stroke: [en.wikipedia.org]
 sfvpool
                                                
                                                Level 7
                                                Dec 28, 2018
                                            
                                                
                                                    sfvpool
                                                
                                                Level 7
                                                Dec 28, 2018                                            
                                        Interesting. I've had a fascination with things European throughout my life. I often wrote a capital Z with a stroke because I saw it used in European text and just liked it. I also write seven with a stroke for same reason. I never realized it had so many varied associations. I did know about its mathematical association.