Well Eppie it is your lucky day.
I seemed to remember I rescued an old Hadcock lift off eBay in bits in the very early days of the site. They are rare, I doubt many were made and I think only in 1978. I bought this years ago and had never got round to restoring it. I bought in England and had it sent to my parents home and brought it to the US after a visit. Anyhow by some miracle this aged brain managed to remember which box it was stored in, even after two moves. I spent and hour or so restoring it this afternoon.
It now works perfectly. The trick was figuring out exactly how it worked as it was not immediately intuitive. It is so rare the Net was no help.
The picture comes up gold, but it is polished chrome. It is beautifully made and a nice example of British engineering of the time.
To mount it you will need to drill two holes in the arm board for those attached brass bolts.
I can't see that I will ever use it. I have a spare Auriol lift tucked away anyhow.
When the arm is down you need at least 1 and 1/8" clearance between the bottom of the arm and the arm board. In the up position the lift raises the arm 1/8" at the point of contact. The lift arm is threaded and acts as the grub screw to hold final adjustment. You can see in the photograph that there is a very small Allen screw that adjusts how fast the arm falls to the disc. You will require a miniature hex wrench set for that adjustment.
Since I have not a clue what it is actually worth, I can let you have it for what you think it is worth to you.
Let me know if you would like it. I would hope this is something you can use and treasure as a unique curio and artefact, by putting it to use. I will be disappointed if it turns up on eBay right away, as I trust you will cherish it as treasure from the past.