I think so, although I think that would usually come with an "a él" to clarify.
I am still trying to absorb the information about object pronouns. "Su coche" as a possessive adjective + noun could mean "his", "her", "their" or "your" car. http://www.studyspanish.com/lessons/possadj.htm points out, "If the meaning of su is not clear from the context of the sentence, a prepositional phrase is used in place of su." Some of the examples they used are:<pre>
María busca a su hermana. (María looks for her sister.) María busca a la hermana de él. (María looks for his sister.)</pre>
If I understand this correctly, if "su" is used in a sentence, it should mean the subject is also the owner or possessor of the object. Then, "They show me their car." is the best translation of "Ellos me muestran su coche."
They show me his car. = Ellos me muestran el coche de él. They show me her car = Ellos me muestran el coche de ella. They show me your car. = Ellos me muestran el coche de usted.
I wrote "They show me his car" and it was correct. If car was plural, it would be sus coches, transl. their or his cars.
Shouldn't it be "ellos me muestran sus coche"? I always understood that "sus" means "their" and "su" means "his" or "her".
I was under the impression "sus" is just the plural or "su" and means more than one object is possessed. "They show me their cars" = "Ellos me muestran sus coches."