Proof of employment or physical presence at a DOE facility, or a beryllium vendor facility as defined in § 30.5(j), because of employment by the United States, a beryllium vendor, or a contractor or subcontractor of a beryllium vendor during a period when beryllium dust, particles or vapor may have been present at such facility, may be made by the submission of any trustworthy records that, on their face or in conjunction with other such records, establish that the employee was employed or present at a covered facility and the time period of such employment or presence.