I'll have to double check that it's not the next size up, but I'm pretty sure. It's hard to keep it straight because IROs tend to have weird measurements (extended seat tube, very slightly angled top tube). FWIW, I did see it sitting next to what I was told was a 53cm Pista and was really surprised at how closely sized they were.

If you're interested, I can take some more precise measurements or pictures for you!