This is one of the areas where "unwritten history" would be nice to know, but (alas) it is forever gone.
We know a lot about the stuff supported by writing (where it exists), such as sales figures and patent records, but surprisingly little about how things like this modification were done. People were too busy making it happen to bother with writing it down, and unless there was some subsequent reflection by the person who actually did the work (or some oral history done down the road and backed up with some cross referencing of similar accounts), the actual process is long time gone, never to be recovered.
We know more about the Roman's extermination of some peoples than we do about how they (to be crude) wiped their asses. Strange. Of course, with the advent of 24/7 (as the kids say) photojournalism and persistent media, we now know way too much about how some people do some things. Better late than never.
Having said that, we still don't completely understand Selmer serial numbers. There's still room for improvement.