According to Sec. V, Art. 6, T-660 and Art. 7, T-762.1 visible light meters shall be calibrated at least once a year. Does this mean that the calibration has to be traceable or can it be simple verification against light meter that has a valid traceable calibration certificate?

For color contrast examination technique:

A minimum light intensity of 100 fc
(1000 lx) is required on the surface to be examined to
ensure adequate sensitivity during the examination and
evaluation of indications. The light source, technique used,
and light level verification is required to be demonstrated
one time, documented, and maintained on file.

This means that the calibrated light meter shall be calibrated from not more than one year. That's All.
Mauro

Also it depends on what your QC/QA system states. For nuclear work (ASME Section III), I would use a supplier approved by audit or holding a valid ISO 17025 certificate with lightmeters in their scope. Otherwise, send it back to the manufacturer (Gould-Bass or whoever).