With the pump pegs on the back of the seat tube, internal brake cable routing, internal routing for likely a Simplex rear derailleur, you likely have a Sport bike from the late 40s. Single ring up front, 3 speed in back and upright bars with the classy bone grips. Having the binder bolt in front is somewhat rare post war, and it reminds me of something. If it comes to me I'll post.
I would agree that the general format of the frame would suggest a 'Sportivo' or sport bike and probably a top model given the internal cable routing such as the 'Selvino' from Bianchi although I am not suggesting this is a Bianchi frame. To help you on your way . . . I took a look at a few old catalogs that illustrated the type of seat lug with the binder bolt above the top tube and ahead of the seat post as follows:
Ganna 1939
Gloria 1941
Maino 1936
Bianchi 1941, 1949, 1950, 1953
Again, not suggesting that this frame is from any of these makers as I am outside of my expertise on this one to be sure. Juvela would know if the Bianchi seat lug was proprietary to them . . . the other marques listed may have used the Agrati product(s).
regards,
Mark