Oh, Crap!, you've been cut off from your friends, perhaps while performing a Last Stand, and have been captured by the enemy. You escape, but how can you prove you're a good guy when the bad guys have been trying to infiltrate your organization, perhaps using stolen or faked uniforms?
Alternately, what happens if, once you make your escape, you need to prove your identity to the local chapter of your friendly neighborhood La Résistance or your own backing organization, but due to the nature of your business, you don't exactly carry company ID cards on you?
Why, then you need a Membership Token! This token is something discreet, yet distinctive, that you use to identify yourself to your fellows but isn't readily familiar to outsiders. It might be some rare or specific item (possibly even some sort of MacGuffin) that not just anyone would have, or something more common but otherwise difficult to get, such as one of a relatively small set of coins with a distinct design.
- In Revolutionary Girl Utena, the ring with the rose crest instantly identifies Utena as a Rose Duelist to her fellow Duelists, and allows entry to the Secret Forest. But Utena herself no knowledge of the purpose of the ring; she had been carrying it for years as a memento of her prince, who said it would lead her back to him. Though the the true meaning of the ring is... complicated.
- State alchemists, in Fullmetal Alchemist, receive specially designed silver pocket watches upon their accreditation. They can show these to non-alchemist members of the military as needed to do almost anything - ride trains without other identification, access their bank accounts, and so on.
- Pirates of the Caribbean:
- Pirates of the Caribbean: The Curse of the Black Pearl: The gold coins from the cursed treasure. Elizabeth Swann unwittingly convinced the Black Pearl's crew that she was Bootstrap Bill's daughter because she had his coin, along with claiming Will's last name (in order to prevent them from realizing she was the Governor's daughter), unaware that they needed the blood of the child of Bootstrap Bill in order to break the curse.
- Pirates of the Caribbean: At World's End: The "Nine Pieces of Whatever We Happened to Have in Our Pockets at The Time".
- It's subtle, but in Iron Man, both Rhodey and Tony Stark wear the "Brass Rat", the class ring of MIT. No particular attention is drawn to it, but it helps to reinforce the idea that these two rather different men are old friends by implying that they were classmates.
- The guys in Chris Cutter's curling team in Men with Brooms all have beaver tattoos. As does Amy.
- In the Wing Commander movie, Taggart is able to earn the trust of the Tiger Claw's captain because he has an Annapolis class ring, from the Class of 1942, specifically a family heirloom of Admiral Tolwyn's, which he would not have parted with easily, indicating that Taggart held Tolwyn's implicit trust. Among the setting's Pilgrims, the Pilgrims' crosses serve the same purpose.
- The A-Team's Army Ranger tattoos work like this at the beginning of the movie.
- The ankh necklaces in Logan's Run are used by runners to identify one another.
- Used in rather the opposite way in Wild Wild West. When Jim and Artemis meet each other for the first time, Artemis is disguised as President Grant. Jim almost immediately works out that he's fake because he's wearing a class ring from Harvard - the President went to West Point.
- The movie version of The Hunt for Red October uses this when the Captain of the USS Enterprise takes a dislike to Jack Ryan disguising himself as a naval officer, until the carrier battlegroup's commanding admiral points out his Naval Academy graduate ring, going on to explain how Jack was in a helicopter crash while at the Academy, and had to finish his studies while in the hospital for his entire last year.
Admiral Painter: Now it's up to you, Charlie, but you might consider cuttin' the kid a little slack.
- E.E. "Doc" Smith's Lensman had the Lens, which glows with light when its owner touches it. It was specifically created due to the need for lawmen to identify themselves with a 'badge' that couldn't be stolen or forged by criminals.
- Randall Garrett's Lord Darcy stories had King's Messengers, who had begemmed badges that glowed red for their owners. This was a Shout-Out to a Lensman's Lens.
- In one The Saint story Simon Templar finds a dead body with a silver greyhound badge on it - the deceased was a King's Messenger.
- In Don Pendleton's The Executioner stories, top Mafia enforcers used aces (playing cards) to identify themselves to other Mafia members. Unfortunately Mack Bolan finds out and often poses as a Black Ace himself.
- In Harry Potter and the Order of the Phoenix, Hermione creates special enchanted gold coins that look like Galleons for Harry to use to communicate when the ''Dumbledore's Army'' would meet to practice the forbidden Defense Against the Dark Arts techniques. They come again in Deathly Hallows to call for aid to the members.
- In One Lonely Night, Mike Hammer finds a card cut into odd angles on the body of a gunman and shows it to his Friend on the Force, who explains it's used as a method of identification by communists, who change the angles on the cards to trip up spies. Before this happens, Hammer is able to use the card to infiltrate a local Communist cell.
- The Animorphs once run into a detachment of Hork-Bajir guards wearing blue armbands, fittingly called the elite Blue Band Squadron. In a later mission, Tobias notes Marco's shirt is the same color, so they rip it up and wear the bands in Hork-Bajir morph. Every Controller stays well out of their way.
- The Horus Heresy novels in the Warhammer 40,000 universe have specially minted medallions, with the makers brutally murdered to cover traces, as proof of belonging to a warrior lodge. As the heresy unfolds, having one can mean the difference between life or death.
- The Kingkiller Chronicle: The Academy famously issues lead "Guilders" to its fully accredited arcanists. They have the advantage of being Loyal Phlebotinum bound to their owners through Sympathetic Magic, so anyone else who touches one has their hand go numb.
- On Babylon 5, members of the Anla-shok, or as they are known to the humans, The Rangers, wear a distinct brooch showing a Minbari and a Human on either side of a large green stone. Earlier in the series, when the Rangers were a covert intelligence-gathering organization, this was used to allow them to discretely identify each other in publicnote Once they become an overt military organization, and even later again become a form of Space Police, it is used as insignia on their uniforms instead.
- While in the books it had no such use (only being used so that Arya can travel to Braavos), the Braavosi coin given by Jaqen H'ghar in Game of Thrones is what allows Arya to secure passage to Braavos and begin training as a Faceless Man, as anyone from Braavos would recognize it as the token of the House of Black and White.
- In Stargate SG-1, since Earth's Stargate has an Iris to prevent any unwanted travellers from coming through, potential allies are given a specially crafted box designed to leave a unique radioactive signature on the iris, alerting them that someone wants their attention. This is later phased out after allies are trusted enough to be given a remote GDO, which also lets them know which friendly wants to come through the Gate.
- In The BBC's Robin Hood, the outlaws have wooden tags with a bow and arrow carved on them.
- In NCIS, in one episode, Tony and Ziva are captured in a mock war games event and met by a man who talks with them briefly, hands them a coin before leaving. Ziva, confused, asks what happened. Tony replies two things, something bigger than them is going on, and two, they will never have to buy drinks at a coin challenge again. The man who gave them his coin? The Secretary of the Navy of the United States.
- Call of Cthulhu supplement The Asylum and Other Tales, adventure "The Asylum". Freygan's cultists have recognition symbols: small stones with thongs for wearing around the neck. They are rarely used since all nearby cult members know each other by sight.
- Dungeons & Dragons. AD&D 2 ed. has some spells working via designated tokens — including "pass-cards" for warding spells and focus for mass mirror image.
- In Forgotten Realms the Harpers have a symbol they use to identify each other: a small silver harp. After the Moonstars did split off, they use their own variant of the same. Cormyr has Purple Dragons' rings and commanders' rings that (aside of minor magics) allow access to restricted and magically protected areas, like the armory in Purple Dragons' barracks. Of course, these items are badges of service and possession of one by someone not entitled to this is a crime.
- Al-Quadim has a lot of secret societies with their own ways of identification; and appropriate magic, like a spell sending a distress call to the nearby fellow member, that works only on someone having a proper token.
- A minor Gotta Catch 'Em All sidequest in Mass Effect had you searching the galaxy for medallions belonging to members of the League Of One, a salarian precursor to the Spectres.
- Becomes problematic in the first game, since with biometrics in common usage and thus negating any need for these, Shepard is forced to routinely wait for people to confirm their identity, that they have Council Spectre status and they possess unlimited jurisdiction. Particularly on Noveria, where a brief stand-off ends with an embarrassed security agent admitting they're a little behind on updating their records.
- After completing the Joining ritual that enters them in the order, Grey Wardens in the Dragon Age universe are presented with the Warden's Oath, a special pendant containing a drop of the blood mixture they have to drink during the Joining. It boosts Constitution a little. The pendant isn't mentioned again after the player character receives his/hers in Dragon Age: Origins, however, and in fact it can be removed (and even sold) in favor of a necklace that has better attributes.
- A major portion of the plot of Metro 2033 involves Artyom getting Hunter's Ranger token (and himself) to Polis so he can get help with the Dark Ones for his home station. By the time of the sequel, Artyom has a token of his own.
- In Quest for Glory II, just before leaving for the enemy-controlled Rasier, the hero receives a sapphire pin from a Katta merchant for free. When inevitably captured in Rasier as part of the plot, the guards remove all your equipment except for the pin, which a fellow Katta prisoner (and leader of the resistance) identifies as a magical Pin of Friendship, which can only be seen by those who would be (or are) friends of the person wearing it. It convinces the prisoner to assist the hero in escaping.
- Lackadaisy has its club pendant, often hidden under a layer of clothes, which is used to get into the speakeasy.
- Tagon's Toughs gain a challenge coin bearing Tagon's profile during the Broken Wind arc of Schlock Mercenary thanks to Murtagh. Since the senior officers have no experience with such things, it takes them a while to adjust.
Tagon: I owe you a drink, specialist.
Liz: A favor, actually. The tradition is spotty here, but there's precedent.
Tagon: A favor then. What do you want?
Liz: Stop being lucky. Start being the sneakiest, meanest, bad-ass spawn-of-a-bandersnatch for ten light-minutes in every direction.
Tagon: So you want me to do my job, then.
- Avatar: The Last Airbender combines this with Secret Handshake: To identify members, the Order of the White Lotus uses a special set of moves on a mah-jong style game. To play said special move, one must be in possession of a White Lotus Tile, and the tiles seem to be used as calling cards for the organization.
- Challenge Coins date back to a squadron of American pilots during World War I. One of the pilots, fairly well-off, decided to have a set of coins minted with their squadron's name on it for his squadron mates to have as keepsakes. One of these pilots was shot down, captured, and deprived of his military identification by German troops. An artillery barrage caused enough confusion for him to escape to the Allied lines, where he was able to prove his not being a German spy only by presenting his squadron's coin to the Allied troops. Ever since then, failure to present your coin when challenged results in a severe punishment. That is to say, you buying beers for everybody who has their coins. Failing a "Coin Check" while in a large drinking establishment can become...expensive. You can be challenged at any time. Even when you're on the toilet or in the shower. It's sacred tradition.
- However, because it can be so expensive (easily running into the hundreds of dollars, depending on size of the group) many commanding officers have started to forbid the practice outright, or at least severely limit it to very small groups of no more than a certain number and only among personnel of approximately equal rank. Bottom line, many junior enlisted personnel simply don't make enough money to pick up a large bar tab without it meaning they won't be able to afford rent or groceries that month. An officer is asking to get his ass chewed to a bloody rag if his C.O. finds out he coined a group of enlisted men and had one of them pay for all the drinks, including his own.
- In the US Air Force, airmen are issued their first challenge coin, called an Airman's Coin, when they graduate Basic Training. Effectively, this means nobody in the Air Force has any excuse at all not to have a coin on them. Those who argue that they don't respond to coin checks because the coin is too important to them are Completely Missing the Point (again, Serious Business.)
- It is very common for specific groups within the military (ie: a particular Squadron or Company, or a group of soldiers who worked together on some endeavor) to mint coins specific to them, or to commemorate special events.
- The rules vary significantly from one unit to another. In some cases, nearly any coin will do. In other cases, it's not enough to have a coin on you. You have to have the senior coin (issued by someone of high-rank, such as a general or an admiral).
- Not everyone is a supporter or participant in this tradition. Many see it as a way for cheapskates to get unsuspecting marks to buy drinks. This is especially true when challenging troops new to a unit who have no way of knowing the rules. Some units avoid this by having the rules specifically exempt those who have not yet been given their unit-specific coin or had the rules explained to them.
- In some fields this is less likely than others. For example, this troper is an aerospace maintainer, one of the first fields along with pilots from the army air core era to practice this tradition. However he never has his coin on him. Why? It's considered foreign debris and can cause mechanical failure. So while coining may be still practiced and said coins are collected, the practice of challenging changes from unit to unit and field to field. This trope was taught that only three kinds of guys do challenges, nonnersnote , cheapskates, and fresh airmen. All of which you don't want to be associated with.
- Graduates from many colleges use their class rings for this trope. People who draw attention to themselves by tapping the ring on their finger against whatever surface is available (tabletops, counters, etc.) are known as "Ring Knockers".
- Many engineers in the United States and Canada wear cast iron or stainless steel rings on the little finger of their writing hand. This way, whenever they use a pen or pencil, the ring will drag across the writing surface and/or bite into the skin slightly (the Iron Ring used in Canada is faceted rather than completely round, unlike the Engineer's Ring used in the US), reminding them of their responsibility as engineers. Of course, the ring also helps fellow engineers identify each other when out in public.