1-Those coats are yours and John's.
2-Those coats are yours or John's.
3-Those coats are either yours or John's.
In which case:
a-All of the coats belong either to you or to John Ithe speaker does not know which is the case)
b-Some of the coats belong to you and the others to John
c-All of the coats belong both to you and to John