It would take some serious meta gaming to remove one of these seals by placing an anti-space time barrier or something >> If one were to legitimately, they'd basically have to win one twice. One to see that it disappears, and another to erect a barrier preventing this (Which most people don't have).
But I don't really want this to be widespread, it ruins the point of a claimed list. I'm fine with counter measures to theft being placed, but these are too much.
Lol, no, no it does not take extreme metagaming in order to do that. Minor metagaming would do.
Seals use chakra. A sharingan even could see the seal whilst fighting the SSM; throw in Byakugan, Rinnegan, and any other sensitive chakra sensory method and you can tell when there is a seal on there. Now, as for knowing what it does, you could claim to have known from a previous victim of the struggle who had the prize ripped away from them at the last moment.
If you really want to get trolly, point out that different seals have different signatures. Someone like Dark (expert particularly in space-time ninjutsu and technique formulas), with a byakugan, could decipher that some sort of space-time effect might happen, among some of the other things listed.
I mean, some minor metagaming is simply the norm nowadays, but it would not take that much metagaming to prepare for the possibilities. After all, if your foe attempts to use some sort of warping technique, that would give you reason to erect the barrier. Or ya know, just in case kind of thing.