This one is diminishingly rare - a real introvabile. IN fact, I have not a single comp in my data. MMMD actually owns one, so maybe you can interrogate him. I'd say it's worth north of USD3000 - potentially far north, depending on condition.
I think LouS is correct about a starting point for the A373x. I've seen two or three on the web. Paul Gavin at Heuerworld has both flavors of this Subsea model.
A seller from Japan was selling his a few weeks ago, it was in very good shape except a tiny little scratch on the right sub-dial, it was selling for $4600 give or take $100. The seller later came to his senses and decided to keep it himself