trimmed reprint scott #40, trimmed proof, or trimmed plate 12 Scott 18.
The secret mark (present on proofs, reprint, and plate 12) gives it away, along with trimming at top, and bright color. Secret mark never present on imperforate plate 1 Scott 5 or 6.
I think this same stamp has been auctioned on
ebay before as a Scott 5, not 6. If I remember it seems to sell always between 2 and 3 grand. I don't think anyone is actually that dumb to buy it. I think its just shilled up and bounced back and forth between unethical dealers. Scary stuff on
ebay.