loose_screws

Hello everyone, This is my first time checking the brakes on my 1998 Legacy I purchased last year. I want to check the thickness on the rear rotors but I don't know the minimum thickness. I believe that it was embossed on the edge of the rotor but the lettering has rusted off. It's not on the inside either, and I don't know the brand either. Is there a standard measurement or does it vary significantly by manufacturer?