Yes, it's O80.
First off, go by "sold" listings on eBay
if you are looking for a valuation guide. Sellers can say anything and offer at any price that they want, and they are not necessarily more knowledgable than you. And genuine sale prices on eBay
are usually somewhere between wholesale and retail prices, probably closer to wholesale for a US #O80.
The pen cancel would reduce the value of this to about a third of its "normal" value. EDIT: A presentation cancel wouldn't reduce the value. But this has the look of being genuinely used. Heavy smudge cancels, though normal, also reduce the value though somewhat less. The stamp is off center (pretty normal also) and has small corner creases and a dirt smudge. It may also be reperforated. Those reduce the value a lot. Now, that's not to say the stamp is unworthy of collecting, but that it's just very low value compared to (say) the Scott value which is for a better-centered and sound stamp.