Check Out This Counterfeit 1914 100.

Look at the faces of Franklin and the allegorical figures - they don't look alive. Look at the shading in "United States of America" as compared to a genuine example. Look at the note borders detail - definitely a counterfeit and not close to the standards of the Russian counterfeits of this denomination.
Still this note does not seem to be legal to own - and would be appropriate for confiscation by the Secret Service.

Here is the law. The Secret Service will confiscate counterfeits if they come to their attention. You almost certainly will not be charged for having it - unless they don't like something else you have been doing - but you certainly won't be allowed to keep the note.

§ 472. Uttering counterfeit obligations or securi-
ties
Whoever, with intent to defraud, passes, ut-
ters, publishes, or sells, or attempts to pass,
utter, publish, or sell, or with like intent brings
into the United States or keeps in possession or
conceals any falsely made, forged, counterfeited,
or altered obligation or other security of the
United States, shall be fined under this title or
imprisoned not more than 20 years, or both.
(June 25, 1948, ch. 645, 62 Stat. 705; Pub. L.
103-322, title XXXIII, § 330016(1)(K), Sept. 13, 1994,
108 Stat. 2147; Pub. L. 107-56, title III, § 374(c),
Oct. 26, 2001, 115 Stat. 340.)
HISTORICAL AND
REVISION
N

I think the "with intent to defraud" and the "or with like intent" clauses allow the wiggle room to legally own counterfeits.

Agree that without intent to defraud you will not be found guilty of the crime of uttering and be subject to imprisonment merely for possessing counterfeit notes (and as I said before unless your case comes to their attention and they don't like something else you have been doing they won't arrest you so you don't have to battle with them over the issue of intent.)
However irrespective of intent counterfeit notes are contraband and are subject to seizure by the feds at any time.
The most famous case on this subject involves the Boggs drawn art notes where there was dispute about whether the Boggs creations were "counterfeits" or art. Some of these notes were actually seized by the government and Boggs sued to get them back. The decision of the courts provides interesting reading. From the decision :
"We need not determine whether the Cheyenne seizure was legal under the Fourth Amendment because Boggs does not challenge the premise that if the seized bills violate the likeness or similitude standards in 18 U.S.C. § 474, they are contraband per se and cannot be returned. Contraband per se comprises objects which are inherently unlawful to possess, regardless of how they are used. As we explain below, the Boggs Bills in this case fall within that category. The district court properly noted that "[i]ndividuals have no property right in contraband materials and contraband materials may not be returned to them." Merletti, 987 F.Supp. at 10. This Circuit addressed the issue in United States v. Farrell, 606 F.2d 1341, 1344 (D.C.Cir.1979):

There was argument about whether the Boggs bills were indeed counterfeits but both sides ageeed that actual counterfeit notes were unlawful contraband and could be seized.

I've been looking for one of these, genuine of course, and have been watching it since it was posted. Just curious of who would pay $1200 for a counterfeit. Since there are 9 watching it, I'm not the only one.

I believe it started out in the neighborhood of $1400.

You can't judge by that 'photo', if you want to call it that. It looks like cardboard. I'm sure it was altered or just plain horrible photography, or a stock pic for that type bill. Besides which, the seller doesn't actually say that's the item for sale. He does, however, say his offering is genuine. If it turned out to be a fake, he surely could be liable. In his defense, though, he does have a near 100% rating after more than 13,000 transactions.