Four tests.
Do them yourself.
Parakh is the goldsmith's word for assay — the test that settles what something actually is. Ask your dealer to run any of these.
The water test
A jar built from Hillwud ply with a glass face, filled and sealed. Watch the joint.
Fill it, seal it, leave it on the counter. Come back the next day and look at the joint line, not the water level.
The knife test
Drive a knife into the glue line and twist.
A weak bond opens along the glue line. A good one tears the wood fibre instead. The scale printed on the board reads FAIL, PASS, EXCELLENT.
The calibration test
High-gloss laminate on half a calibrated sample.
Look along the surface at a low angle, with a light behind it. On an uncalibrated panel you will see the core telegraph through as shallow waves.
The cut test
Cut the sheet. Look at the edge.
Straight lines, even layers, tight glue lines, and gaps that are short and shallow rather than long and deep.