I dug a little in my notes of the time when I acquired the display. My display is most likely a Panasonic TH-50PH10. It seems from what you posted, that yours might be an older screen, if it came with a BeoSystem 1. According to forum posts, the displays started with D5 and then went up until D11. Typing the panel name into an internet search engine, I received the operating instruction manual. If you replace „PH10" with any given number of one of the produced displays, i. e. „PH5“, you will receive the operating manual for this panel.
The manual shows all aspects of the display you are looking for. The IR sensor seems to be for all different panels on the lower left side. Operating it did not require to remove the frame. But I had to hold the remote very close to the frame in a certain spot to switch the unit on or off.
Also, as Lee mentioned, there are connections for passive speakers at the panels rear side.
And the fitting remote per panel is described as well, so best take a look for it in the manual. In any case I attached the picture of my remote (meant for use with a Pana receiver / BD player) and its serial number. Researching the net, I found plenty of it.
In my case, it had been possible to connect an ATV III directly to the Panel. The connection was HDMI from the ATV to DVI-D (panel) for video and, if I remember well, I had to connect the audio separately because of the DVI which did not carry both signals. So, in your case it might be as well the case, that you need an adapter or switch for video and an additional audio connection. In any case it should be possible to connect the ATV directly to the screen.
One hint: I am located in Germany. So, what I found is true for my market and it may or may not apply to yours. As far as I know, there were several variations in respect of the different markets. I remember that there seemed to be i. e. different panel types for EU and US. If it means a difference I do not know.
So, I hope it helps and you will enjoy your BV 4 very soon.
Kind regards,
Rolf
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EDIT: I see that the third character of the S/N is not clear. It is: N2QAYB000338.