Terry's, best known today for its Chocolate Orange, was established in 1767.
Joseph Terry, its founder, was an apothecary by trade, and the firm's early business centred on medicated lozenges and sugared pills - some containing morphine, opium, carbolic acid and cocaine. It was not until 1886 that it began to manufacture chocolate, including the Chocolate Apple, the precursor to its most enduring product.
These Violet Lozenges, produced in 1888, contained violet, otto rose, tuberose, cassie, almonds, sugar, orris root and tartaric acid, and sold for 2s 6d per pound.
The lozenges were exported as far afield as Sydney, Australia, where, in accordance with local regulations, the labels warned that they contained poisons such as opium, mercury and belladonna.
When the Terry's factory in York closed in 2005, the University of York's Borthwick Institute took over its archive, which spans the 19th and 20th centuries.
Other highlights include an original "Oliver Twist" chocolate bar wrapper, menus from the Terry's restaurant and reports from visits to Venezuelan cocoa plantations.
Send suggestions for this series on the sector's treasures, oddities and curiosities to: matthew.reisz@tsleducation.com.