The HP part number for the diodes might actually be 1901-0517 rather than 1901-1517. I really don't know how the HP system works.
See below for a measurement of the probes from my really old HP 8405A for channel A and B. I didn't bother using a narrow RBW or averaging so the plot is a bit noisy once Rp is above about 40k ohms at lower frequencies.?
I think these probes contain the original diodes. You can see that channel A and B both have an input capacitance of just under 2.5pF.
The Rp is 100k as expected at low frequencies and this gradually reduces with increasing frequency (as expected). Both probes agree very closely for Cp and Rp vs frequency.
Sadly, the 'repaired' channel B probe in the newer HP 8405A VVM shows about 4pF input capacitance and the Rp resistance is a fair bit worse up at VHF and UHF.?
