Complex sentence: Mander Brothers was a major employer in the city of Wolverhampton, in the English Midlands, a progressive company founded in 1773 which became the Number One manufacturers of varnish, paint and later printing ink in the British Empire.
Split into simpler sentences: Mander Brothers was a major employer in the city of Wolverhampton, in the English Midlands, a progressive company founded in 1773. In the 19th century the firm became the Number One manufacturers of varnishes, paints and later printing inks in the British Empire.