I have a Flatiron 3MC flat-top octave mandolin, and I love it, to the extent that I know what I'm doing.
I love the tone these instruments put out.
The octave mandolin is part of a sub-family known as CBOM (Cittern Bouzouki Octave Mandolin). The names are sometimes used interchangably, but generally speaking, an OM has a short scale (roughly 19-23"), a bouzouki has a long scale (25" or greater) and a cittern is a long-neck zouk with 10 strings instead of 8. OMs and zouks tend to come from their makers tuned GDAE (an octave below a mandolin) but many are tuned DGAD or ADAD, and citterns may have the same tuning with a high or low course added.
My Flatiron is tuned ADAD, and because the gauge set I need is not standard, I replaced the original stamped tailpiece with one that allows me to use ball-end strings, which are long enough for the 23" scale and cheaper than loop end strings.
There's a handful of models made in Asia that show up with various names, the most common of which is Trinity College. There are also several small builders in the States and elsewhere who build very nice instruments, sometimes at very reasonable prices.
The Mandolin Cafe (
http://www.mandolincafe.com/) has a lot of good info, including its message board. There's also Han's Irish Bouziki website (
http://hspeek.home.xs4all.nl/bouzouki/), which has a lot of how-to pages.
My apologies for the weak picture:
http://www.cpmusic.com/instrument/3mc-front2.jpg
