"On some rence islands I have heard, incidentally, that the men have revolted and enslaved their women. These are usually kept in cord collars, with small disks attached to them, indicating the names of their masters" Vagabonds of Gor
Iron collars of Torvaldsland - Consists of a band of black iron, which is riveted to the girl's neck rather than locked as collars usually are
"Over the anvil lay the joining ends of the two pieces of the collar. The inside of the collar was separated by a quarter of an inch from her neck. I saw the fine hairs on the back of her neck. On one part of the collar are two, small, flat, thick rings. On the other is a single such ring. These rings, when the wings of the collar are joined, are aligned, those on one wing on top and bottom, that on the other in the center. They fit closely together, one on top of the other. The holes in each, about three-eighths of an inch in diameter, too, of course, are perfectly aligned.
The smith, with his thumb, forcibly, pushed a metal rivet through the three holes. The rivet fit snugly.
"Do not move your head, Bondmaid," said the smith.
Then, with great blows of the iron hammer, he riveted the iron collar about her throat." Marauders of Gor
Kur collar
"Over her iron collar she wore a heavy leather Kur collar, high, heavily sewn, with its large ring" Marauders of Gor
String collars of the Red Hunters
"Under the tether on the throat of each there was tied an intricately knotted set of four leather strings. In such a way the red hunters identify their animals. The owner of the beast may be determined from the knotting of the strings." Beasts of Gor
Turian Collar
"The Turian collar lies loosely on the girl, a round ring; it fits so loosely that, when grasped in a man's fist, the girl can turn within it; the common Gorean collar on the other hand, is a flat, snugly fitting steel band. Both collars lock in the back, behind the girl's neck. The Turian collar is more difficult to engrave, but it, like the flat collar, will bear some legend assuring that the girl, if found, will be promptly returned to her master" Nomads of Gor