HP 848x series sensors are industry standard and have been around for over 40 years. Excellent for their stability, although might not have the best dynamic range when compared to modern solutions. When used with care (avoid overdrives) this classic HP sensor design will provide reliable performance for many years for most measurement situations. Just about any reputable RF/microwave test equipment lab (North America) can calibrate them and issue NIST traceable calibration cert.
HP 8482A RF power sensor, came with cable & BNC-M ag=daptor. Tested on existing calibrated HP 435A analog power meter with o dBm reference output, works fine.
RMS type sensor, so accurate (within reason) for all waveforms. 50 ohm Z.