I measured the distortions using my own setup:
1. this oscillator -
https://www.kaltecs.com/ultra-low-distortion-oscillator/2. -70dB active 1kHz notch1
3. low-noise 66dB gain amp
4. -70dB active 1kHz notch2
5. low-noise 60dB gain amp
6. 60/120Hz -30dB passive notch
7. FFA oscilloscope (BW-10kHz)
8. Excel spreadsheet
The measured distortions -> -116.5dB +/-2.5dB
A friend of mine measured the distortion in a local college lab (BW=22kHz AP2700) -> -114.5dB