That isn't a dr. Bristol. It's a loose ring with a copper roller like you said. What are you going to be using it for if you are wondering about its legality? That is also a western headstall, english doesn't use a chinstrap on snaffles and I've never seen one with chicago screws.
I'm aware, but I've never even heard of an english headstall with chicago screws and the crown area is more western as well since it isn't made to have an attached noseband. I was just pointing it out in case the OP was planning on showing. :)
You will need to check the rule book of whatever discipline association you plan on showing with and see if that bit is legal. That headstall isn't appropriate for showing; you will need a proper bridle with a discipline-appropriate cavesson.
If you let me know what discipline/association I may be able to hunt around for some rule books online. Posted via Mobile Device