Brief look inside obsolete Agilent N4691A 26.5 GHz 2-port calibration module for ENA/PNA network analyzers. Modern N4691D version of this same unit is selling for juicy $24312 USD (End of 2024 price).

Internal photo

Poor quality of the business bits also here:

ECAL chip:

Interconnect coaxial port pin at the ECAL module.

Transparency images for the module assemblies