In the shops that I worked in most of the old timers called the gauge blocks JO blocks also. I came across two used C J Johansen micrometers once, a 0-1" & a 2-3". I bought them from a lady who said they had belonged to her late husband. They were kinda dirty with a black grease but appeared in good condition otherwise & she offered them at a good price. I bought them & cleaned them up & they turned out to be the best micrometers I ever owned. I didn't ask but always suspected her husband had been an auto mechanic as he had only the 1"& 3" mics as well as a lot of wrenches etc, which ?I didn't buy. Both of them had insulating panels on the frame where you grip them so the heat of your hand wouldn't affect the reading.
Did a lathe job once which was about a 10" diameter but very thin walls in stainless, forget the exact alloy now. Tolerance was very close for that size. We had a temperature probe that could be placed against a surface to read so when I got to the finish cut I had to take its temp & then figure shrinkage to make that last cut. It worked out just right & was right in tolerance when it got to inspection.
