I tried to find out a bit more about types of wood finish a while back.
It's quite clear that many books fudge the subject because they have no
idea, or only some woolly received opinion, about types of finish.

Basically, _any_ substance that sets hard and glossy has been used to
finish wood.  Traditionally this was beeswax or linseed oil.  All sorts
of mastic and gums were tried to get harder and glossier finishes,
typically dissolved in an oil base.  (This is what 'varnish' usually
refers to -- think of the Copal Varnish used on paintings.)  The oil
oxidises and polymerises to produce a hard finish; that's why alcohol
won't remove it but will re-dissolve the shellac.  Shellac and French
polish came along later (starting a little before 1800).

With the industrial age came nitro-cellulose lacquer, and these days
all sorts of synthetic compounds are used, all of them called 'varnish'
regardless of what they are made of.  The sheer variety of substances
used seems to be the reason why it's so hard to pin down finishes --
almost any combination has been used!  (Does the term 'lacquer' really
just referring to a particularly thin and clear varnish these days?)

I encountered a book, "Repairing and Restoring Antique Furniture", by
John Rodd, written in the 1950s but still available.  The author had
worked since the 1920s.  He described the typical finishes used in
commercial production.

According to Rodd, traditional rubbed French polish -- pure shellac
in alcohol, applied with a cloth pad called a rubber -- was completely
out of use commercially in the USA by 1900, and in the UK very soon
afterwards.  It survived in Germany much later, and at least some
German player pianos (such as Gotha-made Stecks) are French polished.

Rodd says that the USA and UK instead went over to brush or spray
finishes. In the USA a lot of oil-based varnishes were used (these are
the finishes that gum up into little black balls).  In the UK this seems
less common; instead, a spray shellac was used (the same material as
French polish, but sprayed on), such as on Aeolian instruments made
at Hayes.  Cheaper pianos were apparently sometimes given single-coat
finishes literally poured over and allowed to set hard!

The book, "Look for the Dog : Illustrated Guide to Victor Talking
Machines", by Bob Baumbach, describes how Victor moved from varnish to
lacquer finishes in the mid 1920s, largely because lacquer dried much
faster so they had less instruments in the factory drying between
coats.  This reduced tied-up capital and factory damage.  (I don't have
the book here so can't check the fine details so hope I've remembered
that right.)

An interesting subject!  The more I have looked into it, the more
complex it seems.

Julian Dyer