Inception Wiki 's article on Cobb suggests: His Totem is a spinning top which formerly belonged to his wife, Mallorie Cobb.
This is separate from his wedding ring which is a dream based object and thus cannot be a totem.
Which supports the theory of the ring being a dream-only occurrence and not his totem.
I have seen a few theories support that his ring was his original totem when Mal first suggested them.
From that, you can conclude that he took Mal's totem because of his guilt over her death, adopting something in the world that was her's to keep her close even outside of his dreams.
In the overall story, this ring only helps support the purposely cryptic nature of this movie, deceiving and explaining the occurrence of events and objects in more than one way in order to further the ending which is basically to leave the big questions of Is he still dreaming? or What was actually real?
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The ring theory is interesting but I personally find it hard to believe it.
My problem is that I also see conflicting issues with the spinning top.
First of all it is my opinion that the top is a poor totem.
If its sign is to spin forever in a dream, or fall over in the real world it seems too obvious and too easy for someone else to dream that behavior if they have seen Cobb use it or describe it.
Arthur will not let someone touch his weighted dice, and Ariadne has a chess piece who's properties only she can tell - so no-one else can dream the behavior correctly.
These seem like good totems.
This makes me think that perhaps the top is not his totem and that as someone who trusts few people, perhaps the top is a decoy.
Contrary to this however, when Cobb is distressed by the dream he experiences in Mombassa, he wakes up goes into the washroom and spins the top and is interruped by Saito.
If the ring (or something else unknown to us) is his only or primary totem then to perform this display of spinning the top seems unnecessary as he thinks he is on his own - particularly as he seems hurried to try to use it.
If forced to choose between the top and the ring, I would reluctantly choose the top as his totem.
Perhaps he knows something more about its physical properties that we have not seen.
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It is very possible that Cobb used two totems.
His wedding ring and his wife's spinning top.
It's probable that his wedding ring was his original totem.
After she died though he was able to use her totem as he was the only other person to have ever touched it and known it's properties.
I found this really great article that wraps up the questions I had about Inception
http://screenrant.com/inception-spoilers-discussion-kofi-68330/
It makes a bunch of great points and is endorsed by Christopher Nolan according to the site and related article.
The main thing about Cobb is that he obsessively questioned his reality.
So it's very possible that he had a the known totem, a spinning top and another unknown totem his wedding ring.
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The spinning top seems to serve a different purpose from the other totems as it show's Cobb whether or not he is dreaming rather than distinguishing between his dream and someone else's.
So it makes sense that he would carry another one.
Also because he is the best extractor it makes sense that he would be a lot more secretive with his totem.
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Cobb as a character to take you (the viewer) through the movie doesn't have a trust worthy perception of reality.
In my opinion Cobb uses the top to keep Mal locked away, by taking it out and spinning it after every bad dream interaction with Mal he reminds himself that she is dead and it was all a dream.
Its not his token.
He never said it was his token, Arthur was explaining token while he (Cobb) spun the top in the next room.
If you watch the movie, you'll notice that after every non Mal related exit from the dream Cobb glances at his left hand as if he has a watch (which he doesn't have).
I believe he's checking his ring finger.
He only spins the top to assure himself that, yes his wife is dead and yes the real world sucks.
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the top isnt his totem, it was hers.
he would have had a totem if his wife suggested it . .
of course not being the top.
The top helps him decipher real and dream, but kept it has a mememto of his wife as he had to break the secret of his wife ie the safe, he didnt know what it was until he found it then planted his idea all the while knowing what his real totem and state was.
it doesnt matter what his totem was (to us)
so as long as we know that the actions of the top tell us that he suspects he is not in the real world.
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At the end of the movie, in his dreams Cobb lets go of his wife.
His subconscious resolves his issues with his wife, recognizing that she is no longer needed.
And hence, at the end even though he is in his dreams, there is no ring on his finger.
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In Inception, Cobb was wearing his wedding ring in some scenes and in some scenes he doesn't. After watching the movie so many times, according to me, in  every scene of a dream he was wearing his wedding ring and in every scene of reality he was not wearing his ring .  If this is true, what was the necessity of the totem? Instead, he can easily use his ring as totem to identify what is a dream and what is reality.
What's the significance of Cobb's ring in Inception?
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movies.stackexchange.com/users/556/Vijin Paulraj
 It is very possible that Cobb used two totems.  His wedding ring and his wife's spinning top. It's probable that his wedding ring was his original totem. Cobb may have used his wedding ring and his wife's spinning top as his totems. After she died he was able to use her totem as he was the only other person to have ever touched it.
Cobb may have used his wedding ring and his wife's spinning top as his totems. After she died he was able to use her totem as he was the only other person to have ever touched it.