What is "velology"

Velology is the study and collection of vehicle tax discs, particularly of those issued in the United Kingdom from 1 January 1921 to 30 September 2014.

A tax disc was a circular certificate that vehicle owners had to place on the front windscreen of road vehicles, as visual proof that vehicle tax has been paid. Similar systems exist in some other countries, such as in Ireland, but the use of automatic number plate recognition has rendered tax discs redundant in the United Kingdom.

The word is a combination of the acronym VEL, for vehicle excise licence, and -ology., and collectors are known as velologists.