traditionally the PDPV421 is a panel made by sanyo with the following specs below...
Detailed Product Description
Screen Area: 933(h) x 533(v)
Pixel Pitch: 1.182mm(H) x 1.182mm(V)
Aspect Ratio: 16:9
Resolution: 1.23 Millions
Displayable Color: 16.7 millions
Contrast: 3000(brightness full on/off)
Brightness: 1000 cd/m2 (peak value)
Power requirements: AC100v-120v/220v-240v, 50Hz-60Hz.
Power management: 330 watts (average)
but i think there are a bunch of companies rebadging these...some I have seen are Maxent, ILO, and others..
the walmart ad says"PDPV4218HA" for the model number