Scott #39 Used Offered By Large Stamp Dealer. Genuine?

The stamp itself is probably genuine. Images are too poor to determine extent of alterations/repairs, if any. #39 was distributed to certain few post offices, so if you review used copies on the Siegel site and the PF site and find similar genuine cancels, then this is a decent lottery ticket if one can get it for a couple of hundred dollars. However, also take a look at realizations for used #39's on Siegel's site - small faults bring big discounts.
it's amazing that often people will pay more for an uncertified stamp on ebay than a certified stamp from a reputable auction house with faults properly described.

The stamp is genuine, as far as the cancels go... maybe. It also appears that the left margin was added, but that is a bit speculative without seeing the thing in hand.

Tipzi gave you some great advice, and remember that of the less than 200 #39s that the PF has certified as genuinely used only about 25% are also sound. And also take the Scott values with a grain of salt, truly VF examples that are fault free and genuinely used sell for around $6-7,000.

Red flag #1: nystamps

Red flag #2: legitimately used examples are as scarce as hen's teeth and a stamp of this rarity should be certed. Why isn't it?

Red flag #3: I do NOT like the composition/strike of that handstamp cancel. It looks off to me, almost drawn/inked in. The geometry is skewed.

Caveat: This is NOT an area of expertise for me, so take my words with several (hundred?) grains of salt. I'm just giving opinion based upon initial visual appraisal compared to other stamps from that era I have seen.

Simply look at their terms, "Some stamps could be expertly restored, regum, or repaired." Believe them when they say this. I would also pass on this seller even if they had the best deal in town. There are some great sellers online, consider supporting sellers who do a good job and assist our hobby.
Don

A used U. S. Scott #39 needs to come with a certificate from a respected expertizing authority or a buyer's money-back right to seek such an opinion. As has been stated, genuinely used sound #39s are not common.

Rule #1: Never buy expensive singles without certificates. Fakes are not hard to spot, but alterations can be very difficult
Rule #2: Never forget rule#1...

top looks reperfed. I've had very mixed results with this dealer and won't buy from them anymore. Chance of it being a legit cancel: tiny.

I just gave it a fast look. The problem is I can't make out the black circle cancellation. I have interest on the red bar cancel but again while I think it is not right it is hard to tell. I think I see signs of an original hand cancel on the nose. This was a popular cancellation for the stamps however it results in a large drop in value.

However I can't give anything more than no way would I buy this without a certification and to my recollection there have been under 200 certified.

It is a rare stamp to find with a cancellation / used condition.

It appears to have major repair work done in the upper central area; that's why Georges face looks a bit odd. Very visible from the back. Highly doubtful that the cancel is genuine given how much work has been done.

Doomire - I think if you research the SCForum posts over the past few years you'll find some v-e-r-y interesting posts and comments about NYStamps…

"CAVAET EMPTOR."