I started loading back in the 50s and all I had to go by for velocity was the manuals and they were not as trustworthy as I would have liked. When I had access to proper test equipment and a decent lab I designed a chronograph in the later 60s. It wasn't even as "user friendly" as the one described. It had wire screens and it just gave a binary read out that had to be manually converted. At least it told me the velocity and it was more or less correct. Built out of outdated parts and hand wired it had few saving graces. Questionable results meant a trip back to the office and a calibrated scope.
I love my pro chrony. accuracy is close enough and the very occasional failure to read are not a problem big enough to worry about.
