John Grey is a trade mark and is NOT a person. John Grey and Sons was simply a marketing guise to sound like other manufacturers who did use their own names. Why Barnett Samuel did that remains a mystery.
John Grey & Sons Ltd. was a subsidiary company of Barnett Samuel & Sons for the making and selling of banjos, guitars and drums. The banjos were designed and manufactured by Francis Beddard, an Englishman who went to work for S.S.Stewart in America and returned in 1901.
The company started life in London in 1832 as a business which manufactured watches and steel pens and distributed musical instruments wholesale. It was run by Henry Solomon whose father Jacob had come to London from Exeter. Henry sold the musical instrument part of the business to Barnett Samuel.
Barnett Samuel was born in Russia in 1819 and became naturalised British. In 1881, the family and the firm was in Sheffield (They lived at 4 Clifton Gardens) and Barnett, his son Nelson (who joined the firm around 1870) and a nephew Max Samuel (of Prussia) were dealing in musical instruments. Barnett's wife Caroline was Henry Solomon's sister. He also had three daughters - Rosa, Bertha and Minnie who played music together. They all moved down to London as the music business started to take off.
The firm became a huge musical concern selling every kind of instrument including harmoniums and zithers. It became Barnett Samuel & Sons Ltd. in 1901, and sometime in the early 1900's they started making their own banjos after Francis Beddard joined them. By 1911 the subsidiary company "John Grey and Sons" had formed and used the name as a trademark on its instruments. Earlier instruments had just Grey and Sons Ltd as the trademark.
The company made some of their own instruments and had many made by the usual 'makers to the trade' of the time. The badging of John Grey and Sons is not a good indicator of manufacturer.
In 1914, Barnett Samuel & Sons were manufacturing a portable gramophone called the Dulcephone and sold it under the trade name 'DECCA' . Many were taken overseas by soldiers.
In 1928 Barnett Samuel & Sons was bought by British Equity Investment Co. Ltd. but could not use the firm's title. it was renamed as the Decca Gramophone Co. Ltd. The instrument part of the company was contained in just 8 shares of the John Grey & Sons Ltd and these were bought by Rose, Morris & Co. Ltd. who made banjos up to and after the second world war. The company was bought by Grampian Holdings Ltd in 1960 and continued to produce cheap banjos labelled "John Grey". From 1967, the company started selling it's own products and just use the trademark "R.M" from Rose Morris. Rose-Morris are today a large musical department store.
The Barnett Samuel & Sons company also spawned British Music Strings Ltd (1918) and Boyd Ltd, later to become part of Associated Piano Co. Ltd (1927).