I assume you mean #258. You ask a very very good question, especially with the recent numerical grading fad.
It's a nice stamp. But quite frankly, it is not centered well-enough for this particular issue to warrant numerical grading; the grading would unlikely improve the sales price of this stamp to the extent of recovering the cost of the grading.
The general rule I would suggest is that the stamp have a catalog value of >$100, would normally be classified as XF or better, and has at most trivial flaws. As I mentioned in another thread, VF stamps are not hard to come by, and Scott catalog prices are for VF examples.
A few exceptions...
-- if there is a question about authenticity (e.g., in your example, to show it is truly MNH and not regummed), then you want the certification
-- for items >$1000, you might want to consider getting VF graded, just to try to push it close to catalog value; in this range, the cost of grading is small relative to the sales value
The stamp you showed, even though this issue is known for poor centering, would still only be considered Average (AVG) centering. You would really need this stamp to clear all perfs with room to spare, before considering submitting for numerical grading. My opinion.
Nice stamp to have, thanks for posting the pic!

k