Ernie's answer about analog input is right, but vague.
It won't work as a computer monitor because it's not likely that your video card has a 480 interlaced output on a VGA or 5 BNC output.

Even if your video card offers a resolution as low as 640x480, it will be progressive.

This is not a progressive scan monitor, it is a monitor like you would have found in a control room at a TV studio. They may have used RGBHV connections, but it was still an interlaced NTSC signal being routed around.

IMO, this thing probably has a jillion hours on it and probably isn't worth the time and effort you will be putting into it.