The ≡ is a cute idea, but it's a disaster in many ways. You want people to be able to recognize the name of the car so if they see that badge on the rear of the car they know what to Google when they get home (or as they drive :/). Even on this forum, some people call it the Model ≡ and others Model 3. I'm the kind of nerd who has a character sheet right next to my computer here and I still don't remember how to type ≡ (Alt+240) since it's not even Windows/ANSI (most sheets show 240 as ð).
So I'd be happy either way, but I wouldn't blame anyone in marketing insisting they put some sort of unique identifier on the back of the car. Maybe just "Model ≡" on one side and "3-50" or "3-60" on the other.