Same part number, different bin
Panel makers produce one spec and then sort the output. Units that hit every parameter go one way. Units with a bright dot, a faint mura patch, or a slight colour shift go another. Both can legally carry the same model number because the model number describes the design, not the individual unit.
What B-grade looks like on a wall
One panel is rarely a problem on its own. Put nine of them in a grid and your eye finds the odd one in about four seconds. The usual tells are a panel that reads slightly warmer, a dark corner that shows up on a white slide, or a single stuck sub-pixel that is invisible at 2 metres and obvious at 800 mm.
How the sorting gets checked
- Ask for the panel lot number, not just the model.
- Ask for a dark-room photo of the actual nine panels powered on, not a stock render.
- Ask what happens if a panel fails the uniformity check on arrival: replacement, credit, or a discount.
- Ask whether the panels were matched for colour before packing.
Why the 22 percent is usually real
A-grade matched panels cost more because the factory throws away more units to get them, and because matching takes time and a dark room. If a quote is 22 percent lower and still promises matched A-grade, ask to see the matching report. If there is no report, there was no matching.
Where B-grade is defensible
In a menu board behind a counter where nobody stands closer than two metres, a B-grade panel with a faint corner mura is a rational buy. In a control room where an operator stares at the wall for eight hours, it is not. Grade should follow viewing distance and dwell time, not budget alone.