Prinz ref 2069 battery powered shortwave UV test lamp 256nm wavelength for Phosphors of Great Britain Israel USA etc. Requires 4 x AA batteries (not supplied) For detecting Phosphor bands on stamps for best results we would recommend using the lamp in a darkened room, allowing you to see more clearly the difference between the Phosphor section & the normal paper of the stamp. Some Phophors also ;hold; onto the UV light, & emit an afterglow after the lamp is switched off. If you are working on Machin definitive stamps after 1991, when the design of the perforations;changed;you will also need a longwave lamp Do not look directly into any shortwave ultra violet lamps