I think we are getting a few mistakes here, Highbury started by saying he had G19 at .012 " thick at the shaft, I think Gregs 0.120 thou sounds better !, Have you had that end of the box apart ?, Any History of the bike running ? I was thinking , If there was a fault at the final drive sprocket end, It might upset the reading at the clutch end, Just my thoughts, Cheers Bill.
I measured the G19 with a micrometer. It's 12 thou thick, or .012". It's not more than a tenth of an inch.
The history of the bike is a bit thin. I have a 1960 tax disc, and a May 1962 newspaper was found under the mostly dismantled engine. The box was still in situ at that point. Why do you think that there must be a fault at the final drive end? I can add that the bearings have been checked.