Signal Microwave and GigaProbes have developed a line of 40 and 70 GHz test boards. Created as a demonstration tool, they are also used for validating VNA calibration and operation. This helps ensure accurate measurements to 40 or 70 Ghz and they are compatible with all VNA manufactures.
They have three connector to connector traces: -50 ohm -100 ohm -Beatty standard. Other versions include an 85 ohm line, 1 mm pitch probe lines, and LRL calibration lines.