Just found a government report on how commercial lead test kits, even when they indicate a positive for lead, have a significant probability of being incorrect. The same is true for a negative test result for lead.
They recommend sending the sample for test to a lab rather than using the solution(tests requiring liquid indicators) based ones. What also complicates the test is that some forms of lead do not dissolve in the test media leading to no detection and that iron in a sample can yield a positive test. Check out the report below.

BTW I have pictures of the mended brass ring, just trying to figure out how to post them.