Usually it just sneaks up on you... one day you're riding your horse and you think, Darn, he's really well trained... and there you go... he's no longer a greenie. Now to be truely 'made" I think you have to be confident that you can put anyone (with in reason) on him and they can put in a passible effort at whatever the horse is trained to do without the risk of screwing the horse up.
Agree...consistency...my gelding just went from the green to broke category in my opinion. He's pretty much the same every day, in every situation, for every rider. I wuff him!
I would not define it in the context of an "anyone can ride" horse, as I have a "made" horse in my barn right now that very few people can ride (of which the OP is one of those very few! ) I daresay that ULRs have some quite "made" horses in their barns that I would not be able to ride. I took a lesson one fall on a horse that had galloped around Rolex's 4 star course that year, and while I stayed on, I caused him to have stops at BN fences.
The one horse that I "made" myself, I considered had crossed that line about the time that he retired. But, right before we had to retire him, I realized that I could get on, after long breaks in work due to soundness issues and "push his buttons" and they still worked. I would imagine that even today, when no one has ridden him in 2 years, you could get on, give the correct aids for shoulder in, or a leg yield and he'd give it to you instantly.
I had one other that was ridden by a pro (and also, quite well, by the OP! ) and I would not have considered him a made horse until I brought him back to work this year and discovered that he had "buttons" too and that they still worked! He packed my butt around jumping in October and though I made many, many, many mistakes, he tolerated them and took care of us both. Could anyone have ridden him at that point? No, because I tried it with someone else, but I had just enough training from the pro that had trained him, and he had just enough respect for me to not attempt to kill me. And, yes, I still miss the Little Monster a little every day . . .
The other one that I have here that I'd consider "made" is for the same reason, plus he has competition experience. 2 1* long format events in NZ, and all the training and shows necessary to get him to those comps and schooling to go on further. I can get on him, and when I ask correctly (and warm him up correctly!) I can ask and he gives, almost the same way every time.
So, I guess I'd consider them made when they have a combination of showing experience and training and can maintain that training, even without drilling in it.
I used to think of it as a sliding scale in terms of which part of the equation was doing what percentage. At first, with a green horse, the rider is doing 100 percent of the work. As the horse gets more schooled, he or she does a higher percentage and the rider can do a bit less (for example, intead of always setting up the distance to a jump, the horse begins to seek the right spot). One day you realize you're a team where you are each doing half the work!!! Awhile later you realize you have trained your horse so well that he or she is packing you around, doing 95 percent of the job). I like to think I will always hold on to that last five percent of the equation!