Introduced in the very late 1970s or early '80s (it's in the first, 1981, edition of John Walter's The Airgun Book, the first of a trio of italian SSP match pistols introduced about the same time, the others being the overlever FAS604 and underlever Fiocchi P10.
Initially it was sold, or at least distributed in Italy, by Italguns and is fully listed here as the Italguns IGI Air Match CU400, alongside such other airguns as the cheapo Gun Toys break barrel pistols (better known in this country as the Panther).
It's described as "modelled on the well known IGI Domino cartridge pistol", which would have been the FAS 601/602/603, .22" rf and .32" cf target pistols, but I'm not sure if that means it was intended as a target air pistol in its own right, or partly as a training gun (the FAS 604 is described in a later edition as "originally conceived as a trainer, which has achieved success in its own right at national and international level").
The 400 is described as having a dry fire facility ("left side of the receiver immediately above the grip"), the 600 as having a revised trigger and adjustable (instead of fixed) grips (and also being available in a left-hand version, with right-hand sidelever), and the 650 as being a 600 in a foam lined case with muzzle weight and tools.
Iain