Metropolitan Police Special Constabulary King's Crown Cap Badge. UK.

The Metropolitan Special Constabulary (MSC) is the volunteer police force of the Metropolitan Police Service.
It is one of three Special Constabularies operating within London, the others being part of the City of London Police and British Transport Police.
The Metropolitan Special Constabulary have the same Uniform Insignia as the Metropolitan Police.
The Special Constabulary is the part-time volunteer section of statutory police forces in the United Kingdom and some Crown dependencies.
Its officers are known as special constables.
Every United Kingdom territorial police force has a special constabulary except the Police Service of Northern Ireland, which has a Reserve constituted on different grounds.
English special constables have manifested as various legal entities since 1673, but the modern-day Special Constabulary traces its roots to the 1831 “Act for amending the laws relative to the appointment of special constables, and for the better preservation of the police,” which was passed as a response to industrial violence.
1673, 1820, 1831, 1835 saw acts being implemented to establish Special Constables.
The constabulary was redefined for the last time into the organisation which exists today by the Special Constables Act 1914 just after the outbreak of World War I.
In 1949, in a major move after hundreds of years of inequality, women were allowed to join the Special Constabulary.
Special constables generally wear identical uniforms to their regular colleagues.