Kuikka, just curious here, and I make no assumptions or judgments.
I would love to see the three areas here that I've marked with a better image:

The topmost square I added looks like vertical points.

The other two appear to me, like they
possibly could be horizontal.

There is another way to enhance the grill, and there are those on this board that will agree with this, and there are those who will disagree. I learned the technique from Bill Weiss, who passed away a few years ago and was a giant in U.S. Philately, and have used it many times. You scribble from a soft lead pencil on a piece of paper, then rub a finger onto the carbon on the paper and then transfer the carbon to the grill by rubbing your finger on the grill. I've bought many grills that had this done, and have never thought twice about it, and have used this technique and have never thought twice. Others may say that it is enhancing or damaging the stamp.
I'll leave that decision up to your friend as to whether to try this or not.
IF that grill has 14 columns and the points are horizontal, it could be a "Z" grill. I don't think that it is because of the box I added at the top. It is most probably a "E" grill, because I don't see the pimple on Jackson's cheek on the right side of the stamp. The "F" Grill would have a pimple in the middle of the cheek, because it was made from a different relief than the "E" Grill.
The only difference between an "E" Grill (#87) and the experimental "Z" Grill (#85B) is whether the points are horizontal or not. Horizontal- "Z" grill and congratulations. Vertical- "E" grill and still a nice stamp, but with the UR corner the way it is, not much value.
Hope this is helpful, and again, I would expect other responses based on the use of the carbon.
Ray