The Giro was originally for production bikes, but being Italian this rule was quickly so twisted that for 1956 there were two classes - one for production bikes (macchine derivite della serie, aka formula 3) and sport/formula 2, a run-what-you-brung, as long as it doesn't have a fairing or more than 175cc.
The only time Bianchi featured in the F2 class results was the final Giro in 1957 when Franzosi came home 6th (though the Tonale had a great record in the F3 class), which may or may not have been a one-off DOHC racer: but all the film clips, photos and even Bianchi publicity material show the SOHC Tonale, including a Corsa version I'd assumed was the F2 entry. So what's this pic? The one-off DOHC 175 built by Lino Tonti in 1960? But wouldn't that make the bike even more valuable, and of course the Giro as a pure road-race was gone by 1960.
So it looks like a fake, and an example of how well equipped native-Italian "restorers" are...unless you know different?