Shabbat 58 - Servant's emblem
Shmuel stated, "A servant may go out in the public place on Shabbat wearing his master's emblem - if it is tied around his neck, but not if it is sown into his clothing." Elsewhere, however, he said that a servant may not go out even when an emblem around his neck. However, these two contradictory rulings apply to different situations: in one case the the emblem was made for the servant by the master, and in another case he fashioned it by himself.
If it was made by his master, then the master obviously insists on the servant's wearing it, and there is thus no danger that he will remove it and carry it in his hands or pocket. However, if he made it by himself, he may indeed remove it, to hide the indication that he is someone's servant, and continue carrying it, and that is why the Sages prohibited him wearing it on Shabbat.
Then why is it prohibited to wear an emblem sown into clothing? According to our explanation, it should be allowed, at least when it is made by the master? For that we have another reason: commonly these emblems were made of clay, and they could break and fall of the garment. Should that happen, the servant might be afraid lest his master see it and be angry; so the servant would take the cloak off and fold it, hiding the place of the emblem. Then he would be liable for carrying his cloak. Therefore, the Sages prohibited him from wearing such cloak on Shabbat in a public area.
Art: Pieter De Hooch - A Mistress and Her Servant