Q: This girl has met a man online who wishes to collar her. His name is Master[redacted] and he says he trains in the Gorean manner and that this girl would move in with him to be his 24/7 slave. How can this slave know he is Gorean?
A: The short answer is that he probably is not. Even within your three sentences, there are several indicators that immediately raise red flags to those who know what to look for. Let's take them one by one.
1.) "This girl has met a man online who wishes to collar her."
This may well be true. That is to say, he may certainly wish to do so. But how do you know? Did he state this to you? If so, why? Think long ands hard about that conversation. Was he asking for your permission to open negotiations between the two of you? Was he, or has he been, "wooing" you online with attention, compliments, even gifts? No Gorean man would even leave the possibility that he was doing such things in doubt. While a Gorean man may have interest in you, he understands that it is he who brings value to the "relationship", and that while you may be pleasing, you are nothing but a potential slave, and easily replaced. He does not ever ask to be your "Master", instead, if he is what he claims and has an interest in you, it eventually comes to the point that you have no choice but to beg to be his slave. Beware girl, of online doms spouting Gorean platitudes who are looking for nothing more than a girlfriend to fill their lonely lives. Listen to your head, and not to your heart or what lies between your thighs and you would better serve your interests.
And one final thought to take with you: If your entire Gorean interaction has been solely online, it is very possible that you have as yet never met an actual Gorean man.
2.) "His name is Master[redacted] and he says he trains in the Gorean mannner and that this girl would move in with him to be his 24/7 slave.
This sentence is literally oozing with the stink of a dom pretending to be Gorean. First, no Gorean man online will name himself, nor refer to himself as "Master" anything. Why? No Gorean man would think to define himself to others simply in terms of his property. How many "DogOwnerBill"s do you see online? Or "MaytagmodelMHWE950Frank"s? Would you confuse them with a Gorean man?
Understand that the use of the term "Master" or "Mastr" online is a plea from a dom to any subbies he might interact with out there to treat him as a dom, and to please not to be too rough on him. A Gorean man has no need to advertise that he is dominant, it simply is so, whether he chooses to own slaves or not.
There is no "Gorean manner" of training. That is a load of online rubbish. Each slave to be trained is trained individually, as must be. While the potential kajira might well be made to learn traditional Gorean manners of speech and action, rest assured that there is no "kajira manual" that allows anyone to train in "the Gorean manner". Again, this kind of thing is a desperate plea from a dom to submissives to take him seriously.
Finally, you might well end up moving in with him to be his 24/7 slave at some point, but how does he even know at this point in your online conversations that you would be pleasing to him? Does he know that you fart when you are asleep? That you have an irrational fear of spiders? How does he know that you hold any value for him at all? Be wary of such desires stated early in communications, girl. It may well again be a dom, with pretty Gorean words, who is desperately lonely to have someone in his life. So desperate, in fact, that he will at best delude himself as to what he is, or at worst, lie to you about it.
No Gorean man will ask or beg you to become his property, nor will he define himself through you. Understand that the vast majority of those online are simply lonely and in various measures only pretending to be Gorean to find a "mate" that appeals to them. This could well include yourself, girl. Do some introspection and examine your current motivations and desires. Be honest with yourself, and be happy. For the absolute worst thing that could happen is that on your search to end your life's lonliness, you actually do worm your way into the collar of a Gorean man. You will not be there long, and there will be nothing but heartache involved for you.