Yeah, some larger cousin to the mandolin - every string is doubled. If you're trying to replicate it, you can probably just use the more readily-available option: plain mandolin
There is no such thing as a 10 string mandolin. Mandolins are a four note instrument, normally doubled stringed. Eight strings in total, but some mandolin manufacturers decided to add a third string to each course to those four notes. Why? I haven't a clue, but I do remember that my Dad once told me that he tuned one of those doubled strings to be ever so slightly out of tune with the main string. I remember asking him, "Why?" Nuff about that!
The blowup photo, that was posted?
The instrument in question is definitely NOT a mandolin. The blowup photo that spantini posted clearly shows that is indeed a five note instrument.
Zoom in closer to the photo. Pay particular attention to the nut grooves and the wear marks on the frets. Clearly a five note, double stringed instrument. If you Iook close enough, you'll see that there is just one string on the low end.
The 9-stringers I've seen had the 9th string added to the low end as a single string - like a B-string on a 5-string bass. I don't know what the note is.