Interest
It is possible the Walls family were settlers with either the Salters or Drapers companies who settled Londonderry in the 17th C.
The Origins
The Salters' Company is ranked ninth of the Twelve Great Livery Companies of the City of London. Its origins lie in the Salt Trade of mediaeval London, its first licence having been granted in 1394 by King Richard II. Then as now, salt was a vital ingredient in the preservation of food, as it was the only means of preserving meat over long winter months. Members of the Company formerly dealt not only in salt but were also 'Dry Salters', dealing in flax, hemp, logwood, cochineal, potashes and chemical preparations.

The Salters' Company celebrated its Sexcentenary in 1994 and is one of twelve Great Livery Companies of the City of London. The livery companies originated in the trades or 'misteries' (Fr. métiers) of mediaeval London; the Salters' Company, like most of the other ancient companies, had its beginning as a religious fraternity.

Exactly when the fraternity was first established is unknown, but it was certainly in existence early in the fourteenth century. In 1394 a licence was obtained from King Richard II to found a Fraternity and Guild of Corpus Christi in the Church of All Hallows, Bread Street, and to convey property to the Fraternity. At that time, the Fraternity was composed entirely of those who followed the trade of Salter whether or not they lived within the parish, but over the years membership has expanded to include many other professions.

Subsequently, licences were obtained from King Edward IV in 1467 and from King Henry VIII in 1510. Finally, in 1559, a Charter of Incorporation was obtained from Queen Elizabeth. A further Charter was granted by King James I in 1607 reincorporating the Company under its present name of 'The Master, Wardens and Commonalty of the Art or Mistery of the Salters of London' and giving it additional powers of jurisdiction over all freemen exercising the Art of Salter in the City and its suburbs and within two miles thereof. It gave the Court of Assistants of the Company powers of 'survey, search, correction and governance over all freemen of the Company using the Mistery and also over all wares exposed to sale in any way concerning the Mistery and to correct the weights and measures used by the Mistery' within the area. In 1684 the Company was compelled to surrender the Charter of King James I and was granted a new Charter reaffirming its powers and privileges while reserving to the Crown a large measure of control. The Charter was annulled on the accession to the throne of King William III and Queen Mary II in 1689.

Today the activities of the Salters' Company are centred on charity and education. The flagship charity of the Salters' Company is The Salters' Institute of Industrial Chemistry, which was established in 1918 to assist young chemists to complete their training after the First World War. The Salters' Institute now aims to promote the appreciation of chemistry and related sciences among the young, and to encourage careers in the teaching of chemistry and in the UK chemical and allied industries. The Company also administers a number of other charities including Almshouses at Watford and Maidenhead and the Salters' City Foyer Project in Soho, and makes annual donations to over 80 national charities.

The Salters' Company is based at Salters' Hall, Fore Street in the heart of the City of London. As well as hosting Company events, the suite of rooms at Salters' Hall can be hired by the public for banqueting, conferencing or special occasions.

For further information, visit their website, link below.

Origins of the Livery Companies
From the City of London website:

The livery companies probably had their origins in this country before 1066. Guilds (or mysteries, from the Latin 'misterium', meaning professional skill) flourished throughout Europe for many centuries.

The development of guilds in Britain was not confined to London. The Cutlers of Hallamshire in Sheffield, the Merchant Venturers of Bristol and the Fellmongers of Richmond in Yorkshire are examples of those still in existence around Britain.

The word 'guild' derives from the Saxon word for payment, since membership of these fraternities was (and is) paid for. The word 'livery' refers to uniform clothing as means of identification. Today, new companies in their formative years are usually referred to as guilds.

The early companies were the medieval equivalent of trading standards departments, checking quality of goods and weights and measures. They also controlled imports, set wages and working conditions and trained apprentices. After many years of fierce dispute, an order of precedence for livery companies was finally settled in 1515, starting with Mercers at number one.

Notes
  1. The Salters Company
  2. List of the London Livery Companies