Sudarshana Chakra is a type of 'returning' weapons i.e., return to thrower if make no contact to the target. It is quit different from Sikh Chakram in it design, which is, when thrown goes straight(we will leave aside Zena's Chakra).
Difference in form can be readily appreciated if we compare, much older idols of hindu diety vishu with little older relief carving in stone or idols, paintings.
Reprsentation of Sudarshana Chakra can be found at the following links
Sudar?ana chakra - Wikipedia, la enciclopedia libre, Seventh Centry relief found at combodia. Translate the page in english as it is in Spanish.
Stela with a four-armed Vishnu [India, Punjab] (68.46) | Heilbrunn Timeline of Art History | The Metropolitan Museum of Art10th11th century Punjab, sandstone.
God Harihara (half Vishnu, half Shiva), India, 9th century | Flickr - Photo Sharing! 9th Centry, India.
This chakra was held at edge in vertical position with fingers and thumb and thrown with spinning motion.
Now, their are finger spinning chakras of two types, as I have observed, one is the Sikh Chakra(small size) like this;
Sudarshana Chakra - Wikipedia, the free encyclopedia
we all ready know a lot about.
Another one is
Please note that the first digit of finger is only visible, aperture is wide enough to accommodate the finger and no more. Truly mythical depiction.
Between, I recently viewed an image of an amulet (persumbly held by Obama) floating around on Net of Narasimha, 4th avatar, holding a chakra in 'palm' of his hand.
Being older means more close to origin, my take on matter at hand, therefore, Sudarshana Chakra (without the garb of myth, as an ordinary weapon) was different then Sikh Chakra and predates it.
I would appreciate much for any comments or info, whether myth or historical,(please don't repeat already posted in thread).
I might be totally wrong on this.