Someone (can't remember who) has been mentioning the 400 share lot that seems to occur like clockwork just after the bell.

I am sure some have seen this before and not sure if its even true or not but some years back somebody published a list of signals that Market Makers supposedly use between each other using shares , here it is just for some fun:

SIGNALS

100 > I need shares
200 > I need shares badly but dont take it down to get em
300 > Take the price down to get shares....
400 > Trade it sideways based on Supply and Demand
500 > Gap one way or the other, usually to the direction
of the 500 trade. Sometimes -if in the middle -keep the price right where it is".