This exhibit is marked as No. 1, WY2232 and Unit Thermocouple. It looks to be a bolometer for the measurement of non-sinusoidal RF power. The side arms are probably a resonant dipole at the intended microwave frequency and a very small amount of RF will heat the bead and alter the parameters as read from the base connections via a bridge circuit.
The horizontal arms connected to the bead are 37 mm from tip to tip and this equates to a dipole tuned to around 3.3 GHz, a frequency used in centi-metric radar during WWII.
The feint lettering on the clear glass envelope.
The the side arms.
The vertical wires are brought out to the base. The horizontal wires are only connected to the thermocouple bead.
The tiny active bead.
This exhibit was supplied in a paper sack lined with aluminium foil. This was presumably to prevent the non connected device being exposed to an overloading RF field.
The balloon envelope is 64 mm in diameter, and excluding the IO base pins is 137 mm tall.