The 300 Mare Nostrum is a beautiful watch; the watch has a Minerva movement (the balance wheel does look like a big Minerva balance wheel and the 18,000vph is very Minerva), the price is approximately 3x that of the 339. And it's huge, 52mm will just be way too big on my wrist.
At this point, I'm not as enthused about the Mare Nostrum anymore, ultimately due to the prohibitive size and the cost. Furthermore, I really do have to see the movement in person, because at this cost, I am not too far from a Montblanc Villeret Chronograph with the famed Minerva movement I like.
Just an update about the 300 Mare Nostrum.