This sounds like a PDP-504CMX commerical display with an HDMI / component / S-video card installed.
I found the following on Google (I have added emphasis where appropriate):
|LONG BEACH, Calif.--(BUSINESS WIRE)--Dec. 20, 2004--Pioneer Electronics (USA) Inc. announced today the expansion of its family of commercial-use plasma displays, with the PDP-424MV enhanced definition plasma display. This new plasma joins the high definition PureVision PDP-614MX (61"), PDP-504CMX (50") and PDP-434CMX (43") plasmas, offering commercial users another option for their digital signage, boardroom and other business applications
Pioneer currently offers two of its own expansion cards for its plasmas. The PDA-5003 and PDA-5004 optional video cards provide composite, s-video and component terminals for vivid, vibrant images. The PDA-5003 is equipped with stable BNC terminals, and supports an analog RGB signal through its component terminals. The PDA-5004 is equipped with RCA terminals, for connectivity with many external devices.
No mention of an HDMI port with the PDA-5004 video card, however. Perhaps there is something new now available...
Anyway, if indeed this is a 504CMX with an expansion board put in, does that imply there is no TV tuner (NTSC / ATSC) ? If you're going to use this display as a monitor for a STB and DVD player, that should be okay, but you may want to ask if having a built-in SD and HD tuner is important to you.