Learn French: C'est un objet authentique dont le modèle est rare. - It is an authentic object whose model is rare.

We use c'est because it is followed by a modified noun phrase (un objet authentique). If you were describing it with just an adjective, you would use il est (for example, il est authentique). But as soon as you have an article like un plus a noun, you must use c'est.

How does dont translate to "whose" in this sentence?

The relative pronoun dont stands in for a phrase starting with de (of). In French, possession is expressed as "the model of the object" (le modèle de l'objet). By replacing de l'objet with dont, it builds a phrase that literally translates to "of which the model," which is how French expresses "whose model."

Why is there a le in front of modèle? In English we just say "whose model."

When dont is used to mean "whose," the noun that belongs to it still requires a definite article (le, la, les, or l'). You can never put a noun immediately after dont without its article, so it has to be dont le modèle.

If I wanted to say "whose model I love," would the word order stay the same?