Have the retained faceplates been examined against an agreed appearance requirement, with the actual marked regions identified? That should precede the controlled camera comparison; otherwise new settings can make the guesses more repeatable without making them valid reference decisions.
Include a known reject in the comparison, not only the pieces where quality clears a bright band. A camera arrangement that removes glare can also hide a shallow scratch. Better-looking pictures are not necessarily better inspection evidence.
Who keeps the link between those pieces and the new captures, so the next person does not have to identify them by whichever bright feature happens to appear?
Julia's point is now testable with that score. Keep its physical location explicit across the repeated presentations, and record the holder contacts and light arrangement beside the camera settings. Are the different poses deliberate, or is the plate moving when reseated?
And keep tuning images separate from the later independent check. Repeated photographs of the same faceplate are useful for presentation testing, but they do not become a larger physical sample simply because the folder grows.
Another light arrangement preserves the score across our recorded presentations. Reference comparison improved; independent validation set still incomplete.
Will whoever maintains the holder receive those conditions with the reference set, including the rejected view and why it was rejected, rather than only the latest attractive image?