A stamp like this creates an interesting market scenario. A conundrum, essentially, for both buyer and seller.
This certainly appears to be a perfectly legitimate, genuine 7R1E, #5. Almost all collectors do not have this stamp. From that perspective, this is a pretty big deal. Additionally, one of the really major selling points of 7R1E is the full bottom plumes that it possesses. Interestingly, many, if not most copies extant are at least slightly cut in at the bottom, if not very cut in. This one shows the full bottom and then some. That is really cool, from a purist/specialist point of view. One doesn't see that every day.
Now, of course, it is essentially an average condition stamp. We, as stamp collectors, tend to like pretty things that are fun to look at. Some collectors are ok even with major faults, as long as the stamp is pretty.
Back when I was researching and studying 1c stamps, I built up a pretty substantial reference plating collection, in addition to my main, more condition-conscious collection. Many of the plating reference copies were faulty stamps, but I was willing to pay a certain amount for them, as it helped me advance my knowledge and ability to plate 1c stamps. The point is I got a lot of enjoyment from having some 1-margin stamps.
At some point, the question I guess is, where does price become the limiting factor in a stamp like this? At what price will the seller find a buyer?
I guess we'll see (assuming it sells this time).