Noel, could well be. Netherton was the location of he WW2 shadow factory set up to produce Sabre engines, and later (under English Electric’s control) built Deltics. My father worked there as an inspection engineer from its wartime setup (1942/43 ?) until about 1970/72.
Wonder if he ever handled that particular level!!!
I have no idea if it was or not, but i did win it from a UK seller.
I removed the top bezel and found someone has had it off before, the flat screw head should be like the screw at the other end, there is a nut on the other end of each screw that is accessed on the bottom of the level.
After studying the vial I see there are two black socket head screws at the end with the cross vial, screwing these in will raise that end of the vial.
The screw with the lock nut around it toward the top at the other end of the vial prevents the vial moving sideways at that end, and the lower screw is for adjusting the rise and fall of the vial at that end of the level. This adjusting screw has a lock screw coming in from the bottom. Just as Peter said.
I will use my other precision level, which I know is accurate, to get the lathe level then adjust the Watts level.
When I got the Hilger Watts level it even came in it’s black fitted box which has serial #5 Napier Netherton on it so It is the original box.
Peter how far out is your adjusting screw?
Thanks Ian