Like several others on this list, I've owned a number of Masis now (just shoot me and put me out of my misery... ;>), and I'll argue strenuously that the Masis made in Carlsbad from 1973 (or 74, or whenever it was Roland Sahm set up the factory there), to the day the Carlsbad facility closed (1975), are the apex of Masi's frame-building art. As Chuck mentioned, Faliero himself shaped some of the fork-blades on those first Cali frames, and workmanship on those frames is, in general, significantly more refined than on the italian Masis I've seen. The geometry of all GCs--italian and Cali--remained unchanged up to the late 70s at least.
To say that only the italian Masis are real Masis is absurd. An irrational judgement that doesn't take account of the real-world facts.
There is one change that was significant to me: sometime in the mid-70s, I don't know just when, the fork-bend on the GC changed slightly, then significantly. The early Cali frames, and most italian frames I've seen (including a few of the Specials), had the most elegant fork bend, that starts right at the crown and sweeps all the way down to the dropouts. 60s Pogliaghis have this feature also, and it makes for a very beautiful looking fork.
Then, for me, he magic ended with the introduction of the cast lugs. Take a look at a cast-lug Masi and an early Carlsbad Masi, and you'll see the difference at once. Those later frames were very often beautifully made, and the geometry was the same. But the mojo's gone, for me.