A power ring was shown in the JSA Brownstone Museum.
Powers and Abilities
Because Green Lantern didn't physically appear on the show itself, the abilities that he gets from Power Ring are as of this point, unknown.
The full history and origins of the Power Ring are unknown. However, what is known is that at some point, media mogal Alan Scott gained possession of the Power Ring and Power Battery and used it to become the mysterious hero known as The Green Lantern. Using the Ring and Lantern, Scott combated evil alongside the members of the Justice Society of America. However, when the organization known as Checkmate attempted to gain control of the JSA, through false arrests and blackmail, the team decided to go into retirment than remain targets of the government. Alan Scott apparently distinguished the Ring and Lantern, allowing for it to be placed in storage at the JSA Brownstone.
In 2010, both the power ring and the lantern, were found inside of a display case, at the old JSA Brownstone, by Clark Kent. Following the defeat of the Icicle, Carter Hall contacted Alan Scott, suggesting, that he will once more wear the power ring.
Carter mentioned that many of the old JSA member have children and proteges. Alan for example has two children, both of who gained powers due to Alan's exposure to the lantern. 
In the Comics
The Starheart was created Three and a half billion years ago, by the mysterious Guardians of the Universe, to contain the predominate amount of magic they had gathered in the universe.
Eventually, the Starheart became self-aware, as the "Green Flame of Life" and a small fragment of it broke free. The fragment eventually landed on the planet Earth, over a thousand years ago in ancient China. The fragment prophesied that it would act three times: once to bring death, once to bring life, and once to bring power. A man named Chang, made a lamp out of the fragment. Fearful villagers murdered Chang. The lamp, that Chang had made, flamed up and brought death upon those who had murdered Chang. Thus fullfiling the first part of the prophesy. Centuries later an insane lampmaker, named Billings, reshaped it into a train lantern. Afterwards the lantern flamed up and cured Billings of his insanity. Thus bringing new life, to Billings. At some point, in the 20th century, the train lantern ended up, during currently unknown circumstances, in the hands of a then young Alan Scott. For the third and final time, the lantern flamed up and offered Alan its power, thus fulfilling the final part of its own prophesy. Alan used a small piece of the lantern, to fashion himself a ring, that would allow him to tap into the energies of the Starheart. With this power, Alan become the caped mystery man, known as the "Green Lantern".
The power ring grants it's wearer great powers, limited merely by the wearers will power. Some of the powers, granted from the ring include;
- Flight: The wearer is able to generate an aura around his body, which allows him to fly.
- Phasing: Through solid matter (described as the ability to "move through the 4th dimension").
- Energy Blasts: He can project energy blasts as fields of concussive force, flame, water or even ice.
- Energy Constructs: Ability to focus his will and create solid objects such as giant hands, walls and etc.
- Energy Sheath: A relatively permanent personal force-field, that protected the wearer from bullets and the like. This life sustaining aura protects him from harm. He can generate a field of life sustaining atmosphere and protection from harmful radiation, even if he is unconscious.
- Wood: The power ring is powerless against anything made out of wood. Objects made out of wood, are even able to pass through the wearer's personal force-field, thus harming him.
There is another type of power ring. Created by the Guardians of the Universe and used by the intergalactic Green Lantern Corps (which Alan isn't connected to). However, that type is the product of both science and a cosmic being known as Ion, while Alan's is purely magical. It's powerless against anything yellow and can be used as a database. It also has been programmed, so it can't be used directly to kill a sentient being. In the comics it is discovered that the Green Lantern energy is part of the Cosmic Emotional Spectrum of Power. Green is the energy of willpower. If a Lantern's will is strong enough, they are able to overcome the weakness to the color yellow (which is the color of fear).
- Alan's daughter, Jennie-Lynn Hayden (AKA Jade) was born with a natural connection to the Starheart. Allowing her to tap into its energy, without the need for a power ring or having to re-charge her powers, every 24 hours (a feature displayed, in both the GLC power rings and Alan's).
- Alan's son Todd Rice (AKA Obsidian) was born with a contrasting power to his sister's abilities. While Jade is able to create energy and light, Obsidian creates a shadow-like energy.
- Season Nine: Absolute Justice, Part 1, Absolute Justice, Part 2
- Smallville Miniseries: Lantern, Chaos, Continuity
- Power Ring on Wikipedia
- Power Ring on DCAU Wikia
- Power Ring on DC Comics Database
- Power Ring on Green Lantern Wikia
- Power Ring on Injustice: Gods Among Us Wikia
- Power Ring on Young Justice Wikia
- Power Ring on Green Lantern the animated series Wikia
- Power Ring on Batman:the Brave and the Bold Wikia
- Power Ring on DC Movie Wikia
- Power Ring on Super Friends Wikia
- Power Ring on comicvine