You didn't give us much to go on - if will depend on the condition of the frame and it's size, small sizes and bigger frames are worth less. One of the things I have found out about Masi's just because he says it isn't a Californian doesn't meant it's so and just because it has a alum fork doesn't mean it isn't orginal.
A couple of things to look for - what it the tube set sticker, what does the bottom bracket look like and what number are on it, is there a model name. You might educate yourself by looking at several of the sites online that show the various lines and show a chronolgy of when the frames were built. I own 2 Masi 3V'S frames in pretty good shape and I paid $300 and $450 for the other - I was recently offered $600 for one. I probably sell one and wissfully wish I could find a Chris Chance in my size.