We're in agreement that "closest", not "closest without going over" is correct. And I hope that the 10-minute gap rule is going to be workable if a lot of people start putting in their guesses.
Anyway, Matt has the most intimate contact with the db and might have something he can use to edit my post.
I'll let him deal with the issue of "What's market-related?". I know it's almost like trying to define "pornography", but to me it's pretty cut and dry. If the board and post are about the market or a stock, it's good. I wouldn't consider this board a qualifying one.