Thanks for your answers - I have another Tonolini catalogue from the 60ies and there is indeed a 8 gauge offered.
What I'm really curious about is the Fausti connection
I asked in an italian forum and got this answer (in italian, translated by Google translator):

At that time, 1961 shotguns had many rods long and narrow bottlenecks of 10-11/10.
The reasons for these production techniques are to be found in the little seal of borraggi cxercavano that in this way to compensate for the loss of pressure of the combustion gases. In fact, they are also one of the dating bores of the barrels that shoot 18.2 with wads of today create facial trauma to no end.
The company Tonolini, primarily a supplier of accessories and spare parts to dealers, not directly produced weapons but if it was done by artisans of the valley 'Gardone VT'.
the Fausti as other craftsmen have produced for Tonolini certainly, but times were different then and you can not make a comparison with the current production of 'new Fausti'.

Cheers,
Gunwolf