This seems to be a guarded hot box for determining the insulating properties of various materials. A brass tag on the front reads "JOHNS MANVILLE / INSULATION." Inside are two metal vials, one with a "GAERTNER" inscription. The Physics Department at Rutgers University donated this to the Museum in 1966.
Ref: Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus (A.S.T.M.).
Robert R. Zarr, “A History of Testing Heat Insulators at the National Institute of Standards and Technology,” ASHRAE Transactions 107 (2001).
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