Which means absolutely nothing to us, it could still be one of a thousand products.
Mercury vapor is used in many lighting applications, especially where some UV output is needed but the UV light spectrum is very wide and different technologies are used for different parts of the spectrum. For example, I use short wavelength 40W UV bulbs for water sterilization but they are 15mm diameter by about 400mm long quartz tubes with four pins at one end. Some other people use long wavelength Mercury vapor UV lamps for agriculture, display lighting and even skin tanning. Without knowing what kind of lamp you are referring to we can't really help.
Mercury vapour produces UV wavelength of 273nm (UV-C)
That part of UV spectrum gets totally absorbed in atmosphere. Mainly used to be used for UV-EPROM erasing, still used for desinfection in bio labs and hospitals.
Dangerous to retina! Produces irreversible damage, can cause blindness.