Just measured it, it's 62cm. The old thought was the skinnier and higher pressure the tires the better. Now a wider tire with lower pressure and a larger contact patch is thought to roll with less resistance.
The ride was good but poorly attended - it was grey and drizzly all morning, cleared up into a perfect afternoon but it probably kept the people away. There were 3 Marinoni bikes, a Pinnarello and a few modern bikes.

A bike store in Guelph, Ontario, Canada called Backpeddling hosted the ride. If you are in Southern Ontario the store is worth a visit. I had never been there before but the story I got was that they have been there for years and only dealt in used bikes. They started selling a few lines of new bikes a few years ago.
They have a great collection of vintage bikes scattered through the store and sell vintage as well as new. Seem to have a good stock of stuff you don't see much like rigid forks including 1" threaded. They have lots of vintage components for sale (although prices seemed steep) and have bins and bins of take off cheap components like a bike coop has. The price of the vintage bikes didn't seem too bad but tax on top would be the killer.

Backpeddling | King of Bikes – Guelph, Ontario