This crazy-looking contraption is how the U.S. Army researchers measured head sizes for helmets, circa 1973:
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All of these images are from the archives of the Natick Soldier Systems Center Photographic Collection (Natick, Massachusetts is where a prominent Army R&D division is based). Sadly, there’s no further information provided about the contraption.
The Army might’ve done better by modifying the conformer and formillion used by traditional hatters:
Check it out in action here.
Source: core77