So that's what they are, two leaded absolute-zero ice cubes.

Richard, they could be mono-reproducers. This was introduced in the 70's as a
device that could faithfully take an input signal and reproduce the signal at
the output with no distortion, phase shift, and a gain very nearly one. Also,
there was no loss up into the MHZ region. You could take two of these
remarkable devices and have a Stereo-reproducer.
If you cooled a 1" piece of #12 copper to absolute-zero, you might improve on
the mono-reproducer.
73 Gary N4AST