Whilst off work due to my gear box failing on my van I have further scoured the internet and have found the article below from the English Mechanic and Mirror of Science and Arts, Volume 9 (June 18th 1869) pages 382 and 291.
The two companies (name - Smith/family lineage) that are mainly in the frame are Andrew Smith of 69 Princes Street, Leicester Square and Smith (John) of Smith and Turner 50 Bartholomew Close. Whether there is a family connection between these two is still unclear to me, if anyone reading this already knows the answer I would dearly like to hear from them.
SMITH’S patent door-spring, although the first ever introduced for working the door both ways, still continues to keep up its name; there are many places, we are informed, where these springs have been in use for over forty years—for instance, St. Paul’s Cathedral.
The spring has, of course, been improved since the patent was first granted, and differs from all others in the following respects:—The same spring can be so regulated to work a door from l ft. 6in. square to one 9ft. high by 3ft. 6in. wide. The bearing parts are so well arranged that there is little or no friction, thereby preventing wear. It is strongest when the door is closed, and gradually loses strength as the door is opened. It will not stop open unless fastened, thereby preventing injury through being thrown out of gear. It can be made to describe three-fourths of a circle in opening without injury to the spring. The inside spring when in use is never more than a quarter wound up, which allows for a free - and - easy action, and renders it almost impossible to break.
We have so often received applications for information relating to door spring construction that we think the annexed diagrams will be examined with interest by many of our practical readers.
Our engravings show a sectional elevation of a spring with the shoe fitted to a door; the inside of a spring with levers exposed; the sectional plan for showing the inside of the spring worked for retaining the position of the levers; and the revolving pin and socket, as fitted to the door-top."