I picked up an old pump organ. The finish is in terrible shape. You can scratch it to the wood with a finger nail. Don't know what the finish is, but it is probably the original. What do I use to remove it? Thanks!

I'd use a stripper. The ones with methylene chloride are the most aggressive (and most dangerous) but you might get by with one of the friendlier versions.

Definitely use a stripper.   Trying to remove by sanding will only lead to frustration, if not immediately, maybe when you try to refinish.

 

Some reading:
http://www.popularwoodworking.com/techniques/finishing/flexner-on-finishing-refinishing-furniture

 

http://www.popularwoodworking.com/woodworking-blogs/stripping-with-just-the-solvent

A friend used this stuff. He has an 1800's home and is restoring it.

http://www.citristrip.com/

6 hours ago, lew said:

A friend used this stuff. He has an 1800's home and is restoring it.

http://www.citristrip.com/

Citristrip is an NMP-based stripper.   I've used a lot of NMP stripper.  Fumes and skin contact are not (as) dangerous, but works slower.  I usually cover the stripper with a plastic sheet and let it work.

If it's the original finish, it's probably shellac or varnish. Start with the least aggressive solvent you can. That would be denatured alcohol, test a small area with steel wool dipped in the alcohol. I'm betting that will dissolve the finish and you can basically wipe it off. If that doesn't work, go to lacquer thinner, test a small area just the same as before. As a LAST resort go to a methylene chloride based stripper, I don't believe you'll have to do that. I managed a refinishing shop for a few years and that's exactly how I'd approach it.

 

Steve