And going off that example, it's like the difference between a Realtor® and a real estate agent. They both can sell you a house. But one is more respected in the industry, can command a higher listing price, and you have to pay, test and qualify in order to call yourself a Realtor®...
Twaddle. The value of a piece of real estate is not determined by the credentials, or lack thereof, of any real estate weenie that might be involved in the sale. The best that someone could do is try, that's try, for a higher commission based on whatever credentials they might be packing. Good luck with that.
Moreover in virtually every state in the USofA, anyone touting themselves as a real estate agent must be licensed by the state. In most states they must be affiliated in some way with a licensed broker.
A property's value is determined by the market, not who's attempting to peddle it.
I think we should have something like that. "Well, yeah it's $10 sq. ft. because I'm a 'Sign Crafter®' so you know you are getting the very best in quality, materials and workmanship."
Something like that.
To which any rational being would respond, once again, with "Good luck with that." For extra credit please show the necessary and sufficient conditions that would support saying such a ridiculous thing.
The world does not need any more licensing, certifications, guilds, associations, etc. Especially in the sign business. Way back before the most of you were born when virtually all signs were hand lettered, you could either do it or you couldn't. Those who couldn't went of and found other ways to occupy their time. Nowadays, with printers, plotters, and digital design, there is the illusion that anyone can do it. The cold hard reality is still the same; either you can do it or you can't. Them what can't soon move on to the next illusion of a free lunch. While they futilely strive at sign making, they do no real harm and they provide some measure of comic relief.
The same can't be said for real estate jivea$$es, feng shui fruitcakes, interior decorators, and a host of other dubious professions. Yet all of these pastimes have licensing requirements in one or more states, as well as self-promotional associations and guilds. You wouldn't want to engage the services of a unqualified feng shui shaman, would you?
Please state concisely exactly what you want to achieve with some sign makers club. Try to use simple declarative sentences. Further explain why any journeyman sign writer would ever want to join such a club. What possible benefit would accrue to them when they receive their official sign makers badge, whistle, and secret decoder ring?