ATALA 50s-60s?

[dnc1]

I've seen that system with those bars on 'Bianchi' roadsters from the period, but I think those handlebars were used on many Italian bikes.

 

[dnc1]

Here's a 1940 Bianchi.....

...one of several using that system offered that year; "manubrio speciale a leve interne".