The MC95R sensor provides a strong response from Extremely Low Frequency (ELF) through Very Low Frequency (VLF) ranges, with a sharp maximum at resonance near 1.6 kHz. The resonant frequency (usually near 1.6 kHz) may vary considerably due to individual assembly variations and the complex output impedance that the sensor output is connected to. So the calibration data (Vo/field) may differ from your measured results at frequencies near and above resonance, due to different output impedances connected external to the sensor.