Based on my earlier post, I'm still noticing products that get timestamp updates in the data throughout their listing time. It's still just a guess that the update happens when available quantity changes but methinks this is the case. If so, today they've moved 7 TS 55s (with more still available).
It'll be interesting to see if/when something like an LS 130 gets multiple updates considering how rare they are and how quickly they move.