As I understand it, the jeweler's saw was invented (in Europe)
during the Renaissance. It was developed along with a demand for
another recent invention: the clock. Prior to the jeweler's saw,
metal was cut from sheet using chisels. Jewelers had the skill
necessary to make the precision clockwork mechanisms (although very
crude by today's standards), but chisels deformed the gear teeth.
The saw blades were simply a series of chisels in a row, on a steel
blade. Celini probably had this new tool in his workshop along with
another incredible new invention: the drawbench.
I have an old saw frame in my collection. It was made by Morris in
England, around the early 1600s. The blade is relatively short, only
about 3". There are thumbscrews used to tighten the blade, similar
to the modern saw frame, and a tensioning screw at the end of the
frame. The back is not adjustable.
In its day, this must have been just as incredible as the laser
welder is to us today. Since you had to make your own blades, it may
not have been a lot faster to use, but a lot more accurate. And, it
linked jewelers and watchmakers together for over 500 years.