Not that we can trust anything Nicholas says but his reasoning makes a certain amount of sense. Nicholas told Lonnie that the Roswell set was the "Real" set....
NICHOLAS: Better hope you're right. Without Max, no one at the summit's gonna give you two the time of day.
RATH: We're two of the royal four.
NICHOLAS: Royal rejects is more like it.
RATH: Hey, yo, get this straight. We are the originals. They are the rejects.
NICHOLAS: Ha. Uh, gee...they were carefully hidden away in Roswell and got custody of the granilith. You were dumped in the sewer. Figure that out.
The Roswell set was carefully hidden in a cave that could only be opened by aliens. And the Granolith was hidden in their podchamber...
I don't know if Zan would have had the seal or not... I could see him having it, but I could also see him not having it. It's possible that it wasn't Nicholas who approached the New York set to inform them of the conference but someone else who didn't know there were too sets.
Sheeperz makes a good point in the fic "Double Jeopardy III: The Fulfillment"
Sheeperz wrote:"You're lying!" Lonnie shouted. "My name is Lonnie - short for Vilandra! Why else would they call me that, if not because that's who I am?"
"Tsk, tsk, Lonnie. You really aren't very bright, are you?" Max taunted. "What good is a decoy, if you call the original by the name everyone recognizes, and the decoy by a name that's totally foreign?" Max saw the dawning comprehension in their eyes, accompanied by Lonnie's gasp of horror.
It's entirely possible even probable in my view that Zan didn't carry the seal, that his set was known about from the beginning and used as decoys hoping that the real royals would have a better chance to:
Learn enough to use your skills, your knowledge, your leadership to combat the enemy so that you can come back and free us.
This also makes sense why one set was more alien... The more human set could blend in better, stay in hiding longer, therefore possibly have a better chance to succeed.
But what really bugs me about the seal is that if it was used to determine the proper king and the order of succession. Then the seal should have passed to baby Zan.
I know Tess claims he was rejected on Antar because he was completely human, but that doesn't make any sense and Tess was such a liar by that point that we can't take her word as gospel.
If Tess was genetically engineered to be Max's mate as she claimed then any child of Max and Tess should be genetically exactly what Antar needed.
What I think is more likely given what we know of the cannon Tess at that point in the series... is that baby Zan wasn't Max's and she thought she could pass it off as Max's... She didn't count on the fact that any race advanced enough to clone hybrids would be able to run a paternity test and reject it. She figured they'd take her word for it.