KDS Multiscan Color Monitor - Help Please

I have inherited a 19" KDS Multiscan Color Monitor, Part # VS-195e.
It renders a pretty sharp image, but the image does not fill the
screen. There is about 1/2" of black area on both sides & top &
bottom.

The single 'control' at the bottom front center doesn't seem to do
anything. I can't find any other 'control'.

Maybe the 'control' is broke, but I thought maybe someone out there
might have a monitor like this and will surprise me with directions as
to how to enlarge the image. Can I be so lucky?

Thanks