This data hints at a lower peak resonance frequency than 42.6MHz/T, the peak near the normalized 1 (B0/T) - the 3200ps (soak time?), the peak is slightly lower than what is at the exact 1 B0/T magnetization - pushing towards 41MHz/T or so, but at lower B field. Notice also the Peak frequency is moving towards lower frequency as soak time is increased.
More data is needed, however, if this is calibrated data, it is looking very promising.
Also, need to find out if this is soak time to be sure how to read chart.
The Surfer, OM-IV