The last time I was in Sacramento, my friend Maria and I went to Old Town Sacramento (getting there was quite a trick, as I was driving. . .) Among the things in the museum there was this very distinctive mandolin. The sign only said that it was brought to California by Portuguese immigrants, so I assume it is of Portuguese manufacture. I'm sorry I couldn't get a great picture through the glass and all, but have a look! The head is rather startling with all those tuning pegs sticking straight up, eh? Also, the fingerboard appeared to be slightly curved, rather like that of a violin, rather than flat as is usual with a guitar or mandolin.
Here are a few clearer pictures of a similar instrument, though the fingerboard seems to be undeniably flat.