A friend is trying to be a handyman, but for his first job he got into a leaking shower installed in the 50s or so, and extracted a valve stem with an odd washer arrangement:

Name:  Martin's mystery stem.jpg
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I apologize for the lousy picture - it was taken with a cellphone under poor conditions. Anyway, the valve stem is more-or-less conventional until we get to where the washer normally sits. In this device, the end of the stem has a small swiveling piece on it, and the "washer" is quite large -- maybe 7/8" or so -- and is made out of metal with a feature that looks like a spring wrapped around it, but it's not a separate piece. The whole "washer" thing appears to be a solidly machined piece.

In the picture, the washer-thing is leaning on the swively-thing (forgive me for using all these technical terms). I see no way it can actually be attached to the stem, but I wasn't there when it was taken out of the fixture, and I'm glad I wasn't. Any clues? I'll try to get a better picture, with scale, on Monday.

The plumbing is all galvanized pipe, of course, but that's another problem.