2nd question first - tenor banjos are tuned CGDA (jazz) or GDAE (Irish), while the longer Plectrum banjos are normally tuned CGBD

GHS banjos The following extract is from Terry Holland's Web Page

HOUGHTON

George Houghton established his Reliance Works in Heaton Street, Birmingham in 1888 and the range of banjos and zither-banjos he made were branded "Reliance". His well made inexpensive range of instruments quickly found favour with dealers and players alike and before long his factory was extended, his staff increased and the name changed to G. Houghton & Sons and production almost wholly devoted to making instruments for other firms to be branded with the vendor's name and/or trademark.
Houghton's maintained a stock catalogue of instruments (usually marked with a gold-embossed lion with the initials G. H. & S. underneath) with which many retailers and most of the wholesale houses made up their own catalogues. One of the most popular selling lines of their banjos was the inexpensive instruments labelled "Melody Jo". Besides making their own stock instruments they would also copy other firms' prototypes for them, to be branded with the latter's name as "makers".

In 1962, town-planning development in Birmingham plus staff difficulties finally decided George Houghton (son of the founder) to close down and he moved to London to become associated with John E. Dallas & Sons Ltd. The plant and materials and a few of his key workers he brought from Birmingham was established in a factory - at 12 Gravel Hill, Bexleyheath, Kent, and from that time until he retired in 1965 he made the inexpensive banjos sold under the Dallas label.

Cheers
Ray