What about pic related while we're there? I mean, you really want to be that obvious?
As someone who got confronted multiple times to similar situations, with groups that aimed to get a name, symbol, motto, and associated apparel, let me tell you the best course of action: don't, especially not on a public, anonymous imageboard.
If you have a name, people can call you, if you have a symbol, people can't identify you, if you have a motto, people know what you do, if you have neither, well, you're anonymous. How funny is that?
If you really need a way to identify people, there are ways that are certainly more inconspicuous than signet rings, and most importantly, deniable.
- Procedures for discussion. Not just a "secret passphrase", moar liek a way of expressing certain opinions, associate certain ideas, describe things from a specific angle. As an actual example of something I once used:
If a person follows it to the end, it's likely that person is on your side. The odds it just happens randomly are very low, still past that point you should slowly move onto more proper subjects and see how this person reacts. If that person isn't, well, it's just a legitimate discussion, right?
Now that's just the beginning. Freemasons are savvy of those kinds of things, and they have quite elaborate ways of identifying each other. Do note they used to have a secret handshake, but it's no longer in use, precisely because it was hardly inconspicuous and not really deniable.
- Discrete and common apparel. Someone once proposed on 4chan we should just wear a bracelet with four beads on it, out of which the selection is huge. That is the kind of idea that gets somewhere. We can associate colors, shapes and numbers to form something easy to identify, very deniable and hardly random. Most importantly, it isn't tied to a single object, and can be adapted on the go.
- Habits. The way you fold your napkin at the restaurant or your coaster at the bar, get up to greet people, flip your cig between your fingers, fold your shirt's sleeves, iron your pants, lace your shoes… so many details that can easily be changed and allow to precisely identify someone. Deniable as all fuck because who fucking cares about this shit aside from people specifically looking for it?
And that's it. All the groups with matching shoes, swastika pendants, gang tattoos, handkerchiefs, blinders and lapels were swiftly identified, inflitrated and arrested, and I saw their secret identification techniques written black on white in their dossiers. So don't even get me started on ordering this signet ring on the fucking internet and delivered by mail.
If you want to secretly identify each other, don't let just about anyone do it.