Popular since 1850 at minimum, and still made today.
Not just instrument makers, many were made and used by patternmakers who carve wooden patterns for casting metal.
Also general woodworkers use them to smooth curves.
You will never appreciate how useful they are in general woodworking, until you seriously try one for a while. I am perpetually amazed.
I had one I absolutely wore out!! Totally wore out, you don't do that quickly.
I was snivelling, until a friend got me another.
Then I tried to throw out the wore out one??
Couldn't do it, 20 years is just too long.
So I took files and some steel scrap and solder and made a new throat piece for it, returning it to service once again.
I keep several of these handy at all times. Really useful to me anyway,
I like the ones rounded front to back the most. But then, I like curves!
Currently I am looking for some in-between-ers.
Most metal shaves are 10" long, more or less, with a 1 3/4" wide blade.
The little shaves are 4" long with a 1" blade. Again, rough general ballpark.
But there are a few out there in the 6-7" range with 1 1/4" blades and I never had any of those at all.
When you get tired of plain boxy woodwork, spokeshaves are a big part of the answer.
yours Scott