Since you don't know what kind of finish was used, try the
gentle solutions before you try solvents. I'd see what
"Goo Gone" or some other citrus based remover will do first.

wrote:

Unfortunately, I don't know what type of finish was used. I'm assuming
it was varnish of some kind, but I can't be sure. It does not look
like an oil finish (I've used Waterlox on some past projects, and this
finish doesn't seem comparable). And also, I can't try it on an
inconspicuous place first, because only the very top of the table was
affected. The rest of it is still beautiful.

It would be worth stripping and refinishing completely if there's no
other way, but I'd like to avoid that if possible. Any thoughts?
Thanks in advance.