If you've ever been to Tiffany & Co. in Manhattan, they have the doors wide open for anyone. There are a lot of security guards around the doorways and video cameras everywhere.
You can be dressed casual or fancy and they don't care. You can't access expensive jewelry to steal like a smash and grab. The glass is super thick. You would need to pull out a major sledge hammer to crack the glass. A lot of security goes on when a salesperson pulls out a jewelry item to show to a customer so a theft doesn't occur. You can try, but they are going to cock block you on the way out.
You can be dressed casual or fancy and they don't care. You can't access expensive jewelry to steal like a smash and grab. The glass is super thick. You would need to pull out a major sledge hammer to crack the glass. A lot of security goes on when a salesperson pulls out a jewelry item to show to a customer so a theft doesn't occur. You can try, but they are going to cock block you on the way out.