There is no requirement for them to be date stamped, air gun cylinders are under the legal size to be covered by pressure vessel legislation, this issue origanaly came from Germany, where of course they are all stamped, it is not a legal requirement nor an ISSF requirement, the Germans do it for their own interest and a***covering!

Being Italians Benelli will of course do their own thing, in their own inimitable Italian style!
Good shooting
Robin