In 1355 jewellery maker marks were introduced to France, in 1396 England followed by introducing a similar concept. By 1478 'The Assay Office' was established in the Goldsmiths' Hall in the City of London. Hallmarking as we know it today did not come into law until 1973, this is why some pieces are fully hallmarked and others are not.
As shown in the diagram, each mark which has been struck into the metal holds a meaning.
This mark indicates who made the piece, either a jeweller or a company. Researching the makers mark can be the hardest task because the marks were just initials and can be confused with other makers. The Assay Office offer an identification service.
The 'Crown' and the '22' indicate the piece was hallmarked in London and the piece is made from 22ct gold. Other values might include 375 (9ct), 750 (18ct).
In addition to the Crown other Assay offices included Birmingham (Anchor), Sheffield (Rose) and Edinburgh (Castle) to name a few. The Assay Office has four official sites but at one point there were ten.
The letter at the end indicated the year the piece was hallmarked. Each year a new letter with a new font type is issued.
You can look up the letter on your piece at the Assay Office.