A pretty confused thread,here, but the true answer got through.
Anyone can be designated a custodian. Anywhere in the world, of any age. The Regulations call this person a "non-employee custodian".
XXXLAW - Section 2257 - Text of Regulations at (h). There are no qualifications. (Well, definitionally, the person you appoint should not be your employee. If your custodian is your employee, it's a different situation, though the result is the same.) A custodian does not have to be a lawyer or accountant, have a driver's license, read or write English, have a grade school diploma, or be able to see or hear. They may be paralyzed or mentally incompetent. They may be profoundly mentally ill. They may have a place on the Sex Offender Registry. They may be felons or even incarcerated. You can appoint anyone. The trouble is that, if the custodian fails to discharge your duties on your behalf, it is you alone, and never him or her, who faces criminal responsibility.
But, like the posts suggest, using a third party custodian is dangerous as hell. You are putting your gonads in someone else's hands. Hands which always rest on the chopping block. You can't contract away your duty as a producer to anyone else. The 2008 changes that permitted third party custodians merely afforded producers another way to comply. Those changes do not shift responsibility or criminal liability. If your custodian screws up, you are the one to whom the law turns, the one who gets punished - perhaps sent to prison for five years - because compliance remains your responsibility, no matter with whom you have hired to do the job. Third Party Custodian or employee who does the job, notwithstanding. It's always about you as Producer.
If the matter you publish does not contain depictions governed by Section 2257 or 2257A, there is no obligation to publish any kind of disclaimer. While it is your option to do so, you don't ever need to publish a statement that the images are too old to be governed or that the material isn't regulated by the statute. Depictions of boobs alone do not implicate Section 2257. But sex itself is not necessary before the statute applies: actual or simulated images of the genitals or pubic area, of sadistic or masochistic abuse, and/or bestiality are enough. A naked lady in handcuffs in a sexualized context is probably enough.
The latest lawsuit challenging this law has now been in the trial court twice and now has bounced up to the Third Circuit for the second time. It is fully briefed and oral argument was conducted in December. Eventually it will render its decision. More about that lawsuit at
XXXLAW - Section 2257 - 2257 HOME PAGE