I found a very old guitar 6 strings maybe from 1900 and on the inside
it says Columbia Guitar Unexcelled at the price Is it worth anything?

Bobbie,
This is no answer, but I seem to remember that guitars  - even
excellent guitars -  don't last for ages or improve with age, in
contrast to great old violins, violas, and cellos.  If this
recollection is correct, I can only speculate that the reason relates
to the flatter surface of guitars and perhaps to different stresses
from the way they are played.

I was given a guitar that matches your description exactly.

It has 6 nylon strings with a parlor body; mother of pearl inlay (or
imitation) of a single circle at the 5th, 7th, and 10th frets; a metal
bridge; a white (plastic?) peg (for attaching a strap) at the base of
the body; black (plastic?) tuning pegs; and a round neck.

Inside the soundhole is a circular paper label. Following the curve of
the circle, printed across the top, are the words COLUMBIA GUITAR in
all caps. Following the curve across the bottom, in smaller print, is
the slogan UNEXCELLED AT THE PRICE, again in all caps. The label is
very light blue, almost white. The text is red.

In the center of the label is a full body portrait of a greek/roman
goddess (liberty?). She is wearing a white dress with the "skirt"
portion in blue with white stars (to match the US flag) and a sash in
the same print. She is holding a flagpole as tall as herself with a
very large US flag falling loosely to the ground.

There is no other text: not a year, not a city or country name, not a
model number, not anything: on the label. I am very interested to know
in what year and country this guitar was manufactured.

Good luck with identifying your instrument Bobbie.