key for ATC-510

Hello,

We just found an ATC-510 in our high school science storage closet (we
used to teach an aeronautics elective for seniors). There is a keyhole
on the front lower left panel, but we do not have a key for it. Should
the panel light up/operate without the key in place? I'm trying to
figure out if the panel still is functional or if I need to find a
replacement key. If I do need a key, does anyone know how to contact
ATC for a replacement, or does anyone have one?

Thank you for your help.