Stamp ID Helps For 3 Cent Washington A25

these are my last 4 3 cent washington a25 with grills.

i just would like to see your opinions on the grills.
this is about the best I can scan for now.

i always thing that the more heads the better.

The top two appear to be E grills (14X17 points) and the bottom two F grills (12X16 points) but it is difficult to tell from the scans.

One thing I've done that brings out the grill points very well is to rub a pencil on a piece of paper and then gently rub the paper with the graphite on it across the grill on the back of the stamp. This makes the points much easier to see, count and measure. Once finished, I soak the stamp and most, if not all, of the graphite will wash off.

thanks for your help.
i will have to try your method.