According to my research, the makers Hampson and Bettridge were based in Old Bailey, London, from 1861, so no older than that. It was used until 2004, in the Bindery of a company founded in 1804, so it's probably over 100 years old. It weighs 25lb. The wooden threads are worn, but still do the job.
Dimensions:
Jaw length 1 ft 9 and 7/8 inches/55.5cm long
Jaw depth(front to back) front is 12cm (it's been planed on the inside at some point in it's life) back is 12.3cm
Jaw height 5 and 1/4 inches/13.5cm
Distance between the 2 screws 1 ft 4 inches/40.6cm
Length of screws 1 ft and 5 and 3/8 inches/45cm
Too heavy to post so collect in person only.