A year ago I would have said you got a screaming deal. But if check ebay prices very recently, like the turquoise 61cm or so that just went for $900, with the paint in good shape, maybe not. Really depends if you fit it. The big bikes don't come up that often but the big guys are stingy. All that written, the twin plate crown bikes are more desirable. There will be a frame number in addition to the size. A quick look at the Masi registry only shows two 63cm bikes, that does not mean too much, but good chance they only did one or two runs of 25 in that size.
A good repaint will set you back, $500 at least with a full transfer set, original paint will be more valuable for resale in all but the poorest condition.
If it fits, keep it. If not, look for a better fitting mount in a color you want more. Either a frame or complete bike.
Original equipment was Full Campagnolo, Martano rims, stainless spokes, small flange hubs, Cinelli #2 saddle, Clement seta tires, Masi foil stamped Silica pump, Masi waterbottle. Last Masi Gran Criterium waterbottle (NOS) I saw sell on ebay was for almost $200. Everest chain and freewheel, 5 speed in back.
Masi measures to the tip of the seat lug from the center of the bottom bracket.