The turret is not an automatic indexer, you have to turn the turret by hand then lock it in place with the handle.
The serial number is on the flat around the spindle lock, and is 1020/1 if I have it correct it may be from the early half of the 1930's

The machine was originally owned by Flight Refuelling Ltd, which make air to air refuelling equipment for military aircraft, I wonder which parts this machine made.
For the last ten years it has been used by a small engineering company in Reading, for small runs of parts.

More pics to follow