Standard fluorescent UV lamp.
The fluorescent lamp with a shade so that overhead lights don't 'flood out' its effects.
Read all about how UV light works; see lots of photographs of what you will see with UV light, click here.
Wavelength: unknown, probably about 365mn
Lamp: standard fluorescent tube.
Overall size 6.5 X 1.75 X 1.5 inches (165 X 45 X 35mm)
Tube size 5 X 5/8 inches (130mm X 15mm)
Power: mains only (4ft cable + plug included)
More info, more pictures
Click on the picture above, see the security markings on an old (pre-2017) twenty pound note,