origamigoldfish

I recently found a deal on a Standard Rotary Slim Machine that I just couldn't turn down. I spent sixty dollars on a machine that had no rust on it and the treadle worked well and the needle moved easily when I turned the hand crank. It's not in great cosmetic shape; the usual cracks and uneven finish on the cabinet, and I think the machine itself is missing about 95% of the decals. I am looking for a machine to use not display, so that's not a big deal to me.

What is confounding me is that there is some kind of gunk covering the head of the machine that I just can't get off; it's a rough covering over the arm and base of the machine, and there are drip marks that I am thinking is not the original finish of the machine. It has a hard finish, and isn't sticky like the old oil and grime I've been cleaning off the working parts of the machine. On the base(deck? my first sewing machine since I was a kid, still learning the terminology) the stuff is thin enough that I was able scrape a little off with my fingernail. It came up a gold/orange color, but looks black on the machine. Is it some kind of varnish or shellac that someone applied years ago to protect the finish?

I haven't had any problem cleaning the working parts of the machine, but I can't get this stuff off the head. I was able to soften what I scraped off by soaking with a hot, wet rag, but that's not an option for the whole machine. Will sewing machine oil be able to soften/dissolve the stuff if I leave a layer of it on just to soak, or do I need to break out something else? If the decals are still there and just hidden under the gunk, I'd like to save them if I could.

I have major reactions to most cleaning fluids, and would like to avoid kerosene fumes if if I can.

Any advice would be greatly appreciated.

Thanks!