I'd love to know more about how/why you all clear users. My assumption is that users can register themselves and will stay with a clearance of "No" for any duplication requests. And once they come into the building to enter the reading room, you check their ID and mark them as "Yes". But that means you can have hundreds or thousands of valid uncleared users.
Would it be better to have multiple clearance levels? What would those look like? Are there people who would move back and forth between cleared and not?