Italian, yes, but the diagram is very informative. I've never seen an action with gears and a split piston assembly. What is the advantage of that? Maybe a smaller cocking lever stroke or reduced cocking effort?
The purpose of the double pistons is to negate each other's recoil. The old Dianas are, IMHO, the most truly recoil-free spring-piston target guns ever made. You will swear you are shooting a pneumatic.
The Diana barrel-cocking models 60, 65, and 66; and the fixed-barrel sidelever model 75, all use the same system.