The grills can be seen on either side of the stamp, although most clearly on the back of the stamp. It looks like a waffle. You may only be able to see part of the grill. The stamps were impressed onto the stamp several sheets at a time. The top sheet would have had sharp clear grills, whilst the bottom sheets grills would have been faint and hard to see. The sheets were not always fed in vertically aligned into the machine, therefore it is common to see only part of the grill. The more defined the grill the better the value.
