Mineral spirits, huh? I'll definitely give that a try! If there is a wax buildup, will this remove it?
Don't worry, Henry, I have no intention of using water on these cabinets at all - at least not until I'm sure of what I've got and protected them adequately! (and then, only a damp cloth as needed to remove spills).
I had planned on doing an alcohol test once we were moved in to verify that it was shellac, the landlady was so young when the house was built that although she remembers her dad saying they were shellac, I can't rely on that! *grin*
Not that I'm an expert by any means, but I don't think there's any wax or polish of any sort on these cabinets. Like I said, the kitchen was used only rarely (once or twice a year) from the early 40s to about 1990 (they had a second kitchen downstairs that was the one preferred by the mother). The intervening tenants may have done something, but it really doesn't look like it.