The important point to be observed here is that you use the NOUN only when your hearer can be expected to know which NOUN you are talking about because either a) you have already mentioned it, or b) you will define it as soon as you have named it, or c) it is common knowledge the two of you share.
- A seller placed his knives neatly, (1.1)another / (1.2)the other placed various pottery in disorder.
In set 1, (1.2)the other is probably ungrammatical. This expression implies one of a pair of sellers you have already mentioned. But the first seller cannot have been identified before you mention him, since you speak of him with the indefinite determiner; this implies that you have not mentioned the pair. Consequently the second seller cannot be the other of the pair: he can only be (1.1)another seller.
In set 2, (2.2)the others may be grammatical or may not. Some determines an indefinite number of sellers, but it does not imply that the sellers belong to a group which you have already mentioned; consequently some may be applied either to previously undefined sellers or to members of a previously defined group. If you have already mentioned the entire group of sellers, then the others is grammatical: it designates all of the group who did not place their knives neatly. But if you have not mentioned the group, then your hearer does not know the group of which they are members, and the others is ungrammatical.