Guerc 

It makes sense but probably I'm not going to be successful. I found it down the CA coast from me (probably explains the flash rust) inland from Santa Cruz / Monterey. It was less of an estate sale and more of a garage sale. My wife pulled me in for the furniture on display when I spotted the bike. Everything of value was out on the lawn, and it looked like the family just wanted to clean out the house and donate the rest. I think perhaps the owner passed away a while back, then his spouse passed on recently, since there was a lot of cooking / canning / quilting stuff but not a lot of "men's" stuff left. It is sad what we leave behind.

There was some aviation stuff (manuals, books, etc), but nothing else cycling related. I'm pretty sure I asked for anything else, but I also just wanted to get out of there before someone else saw what it was. I was on a trip with with my wife, and I had to drop the rear seats to fit it on top of our luggage. She humored (for a while) my excited rambling about "historically important" and "Mario Confente came to America to build this bike" and the plotline of Breaking Away. We then had a long drive home pretty much in silence.

I've seen your pictures on Brian Hovey's site - such great memorabilia. He has a great serial number decoder on the site too. From that, and from inspecting the bike, I think it is a "typical" Masi of the day. There is no evidence Mario Confente ever touched it (would have 4 vent holes instead of 1, Mario's "C" mark stamped in the steel, etc). The Serial number has an alphanumeric code and letters, which I've also heard indicates whether it was built in-house or subcontracted.