That will be 100% ineffective. It will never be admitted in court. That procedure is not written into copyright law. How do you even argue the so-called original is actually the original?
What you want to tell the offender is that you have registered it, and which should easily eliminate any problem. Copyright court will be very expensive, but winner can claim damages to cover their part, plus even punitive damages. They will be NOT willing to risk this, unless they are in the right, and you are the offender, and they have the early copyright.
So you have a photo image, or a written novel. And someone else also has a copy of same. How do you prove you created it? You really can't. It is all you said, they said. Normally it is simply not feasible to argue these details in court, because there is no hard evidence, it is always you said, they said. Such arguments are not accepted into court. However, copyright law provides the solution. You register your work - send a form and a copy to the Library of Congress, who keeps records when they got your claim of creation. And without registered copyright, the courts will not consider the case.
Now the argument is: Who registered it first? And the Library of Congress provides obvious evidence of that proof.
You hope they did not register your work before you did (they easily could have). But you had easy first opportunity that only the creator has. The court argument may come down to is it the same work (which experts probably could decide an opinion), but there is is no dispute who registered it first.
That is how the system works. Any other copyright nonsense heard on the internet should be disregarded. If it is important, register it, NOW.
See US Copyright office
http://www.copyright.gov/circs/circ01.pdf (copyright basics)
U.S. Copyright Office - Frequently Asked Questions (frequently asked questions)