The Royal Warrantm as it is known is awarded to businesses that supply
goods to members of the royal family.
From the Royal website:
http://www.royal.gov.uk/MonarchUK/Symbols/Royalwarrants.aspx
Royal warrants are granted to people or companies who have regularly
supplied goods or services for a minimum of five consecutive years
to The Queen, The Duke of Edinburgh or The Prince of Wales.
....
Each of these members of the Royal Family can grant only one warrant
to any individual business, but a business may hold warrants from
more than one member of the Royal Family.
Advice on granting warrants ....
The warrants are a mark of recognition that tradesmen are regular
suppliers of goods and services to the Royal households. Strict
regulations govern the warrant, which allows the grantee or company
to use the legend 'By Appointment' and display the Royal coat of
arms on his products, such as stationery, advertisements and other
printed material, in his or her premises and on delivery vehicles.
A Royal warrant is initially granted for five years, after which
time it comes up for review by the Royal Household Tradesmen's
Warrants Committee. Warrants may not be renewed if the quality or
supply for the product or service is insufficient, as far as the
relevant Royal Household is concerned.
....
Warrant holders today represent a large cross-section of British
trade and industry (there is a small number of foreign names),
ranging from dry cleaners to fishmongers, and from agricultural
machinery to computer software.
Some firms have a record of Royal warrants reaching back over more
than 100 years. Warrant-holding firms do not provide their goods or
services free to the Royal households, and all transactions are
conducted on a strictly commercial basis.
....
--
Peter Duncanson, UK
(in alt.usage.english)