When a silicon diode reaches 0.6 V we call it "saturated" and then the slope becomes the bulk series resistance ( or as I like to call it, the incremental effective series resistance , ESR.
The ESR. is the almost linear slope after 0.6 V but current ratings are often given for Vf=0.7V or Vf @ xx amps, as the transition zone for lower than rated currents e.g.10% If max tends to be in this range from 0.6 to 0.7 drop ( almost like a 1.5V battery voltage ranges from 1.3 to 1.6V )
If Vo = 49.3V max then for any given diode we can compute the current that causes a 0.7V drop or choose a diode datasheet and get these parameters.
Here is the common 1N4148 small signal diode curves with more details from the datasheet.
See if you can find the current approximately (as there will be a tolerance for all parts ) for the forward conducting voltage Vf=700 mV .
Using only Fig 4. as this small is rated only for 10mA DC for heat reasons.