limit is not the same as..
..
aon (all or none)
you can say, buy 100 shares at a limit of .005 but with it being allowed to fill in parts,, but aon means its just that .. all or nothing.
i never use aon, nearly never, cause it may not fill, its too hard for the mm to deal with an aon in low volume.
make sense? also, you cant buy market in penny stocks, you can sell market but not buy.. so you have to put limit price anyway. :-)