Barographs?
I've two old Peravia barographs - with a couple rolls of paper. These were very elegant mechanisms that punched a tiny perforation in a continuous roll of waxed paper every 6 seconds. The drums marked the paper for time so that it was possible with a Peravia to record both altitude and the exact time of the altitude. The paper became quite scarce but it could be made out of household wax paper. Free to a good home. You pay for shipping.
ROY
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