I assume that Ferrania evaluated the ISO by the ANSI standard.
Simplified, a step wedge is exposed and the film is developed, in a developer very similar to D-76, to a certain contrast (slope of the characteristic curve). The ISO is then determined by evaluating the curve close to the toe:
https://www.kodak.com/uploadedfiles...en_motion_education_sensitometry_workbook.pdf
Thus, developing according to the standard gives every film a contrast withing a certain tolerance.
The contrast specified by the standard aims at fitting a scene consisting of 10 stops of light on the useful part of the characteristic curve. By useful, I mean on a part of the curve with enough slope to show detail and that can be absorbed by a photographic paper.
This must be the starting point for any comparison of developers or for modifying the curve to accompany a scene with more or less than 10 stops of light.
The good news is that you do not need any advanced sensiometric analyzers to do this. You simply need stuff you already have: a camera, an 18% gray card, a couple of films and means to develop the film and possibly (but not necessary) make prints:
http://www.halfhill.com/speed1.html