d2dd4b77___Stamp_Collecting_Accessories__Description
[Accessory] Ultraviolet Light [Price Range] $20 [Description] 
This is a more recent entry to the stamp collector’s arsenal. It helps with detecting luminescent coatings on stamps issued after the classic period of 1840-1940. Most of these coatings are invisible to the naked eye (tagging) but visible under ultraviolet light.
One Family's Blog: Stamp Collecting Accessories
Description