Anywhere from $5 to maybe a lot more.

Without a proper description, it may be junk or may be ok.

"works" = makes a noise...

"keys worn" = make the instrument worth little, as

1) if 'fixed, then the instrument is no longer totally original, so the collector value is massively reduced.

2) to attempt to 'refurbish to original condition' will be expensive

"otherwise very very good condition" = they all say that - just like all the prisoners in jail are innocent.... :-)

If provided with an excellent documented provenance that can be proved and it is a very rare unusual example, it may be valuable.

Those made '100 years ago' are not particularly valuable as a playing machine, as the acme (golden age) of the instrument was after the 30's - peaking in the 1960s, when the quality of the machines was at their peak.