It seems to be a secret organization, but nobody knows for sure. It is a suspicion of many intelligencers (spies and intelligence organizations).
If one travels, you might notice it. These merchants often specialize in foreign goods, but often buy local produce and products, to trade in other places. In larger cities there will be one to four merchants. In cities or towns there might be one. Many of them seem totally unrelated to the others. Yet they are marked.
Each one has a blue orb on their signage or somewhere in the shop. (In places where the world is known to be round, it will be a globe). The various blue orbs in the shop might be a blue baseball/ cricket ball sized orb on the counter or near the till, a blue ball latern, a blue crystal suncatcher, or blue spot painted on the wall. If shop windows are available, often time the blue sphere will be visible from it.
If pushed, they will say that it is a lucky symbol for certain merchants. If pushed a bit farther, they will say that certain trading companies (foreign usually), will award the blue sphere to those they have had “good dealings” with. By displaying it, they advertise to those of the trading companies that they are good partners.
(Note: If a merchant justs posts up a blue sphere to try and attract the traders, and has not earned it from them, said merchant will often have “accidents”.)
A GM should just drop these clues from time to time. The players will probably investigate the apparent “red herring” and find nothing.
Merchants of the Blue Orb, though they do not call themselves that, have a secret. They are Travellers, beings who have traversed the ‘verse. The people of the blue orbs will use their “public fronts” to trade good across the ‘verse, all under the guises of being merchants who work with foreign traders. These travellers protect their secret, their advantage, jelously. They will go to any lengths, except those that would reveal their secret, to protect it.
The Blue Orb is a signal to other Travellers that this merchant is one of their own.