Thomas Thalric Harman, Showell's Dictionary of Birmingham… (1885)
“ Glass.—In the reign of Henry VI, the commonest kind of glass was sold at 2s. the foot, a shilling in those days being of as much value as a crown of today. The earliest note we can find of glass being made here is the year 1785, when Isaac Hawker built a small glasshouse behind his shop at Edgbaston Street. His son built at Birmingham Heath on the site now occupied by Lloyd and Summerfield. ”
