Which word describes a model of excellence or a peerless example?

The term "paragon" specifically refers to a model of excellence or an ideal example of a particular quality or characteristic. It signifies something or someone that embodies perfection in a certain aspect, setting a standard for others to aspire to. In this context, a paragon is often used to describe a person or thing that is exemplary or serves as a benchmark, illustrating the highest level of achievement in a category. This makes it the best match for the description provided in the question.

On the other hand, "prototype" is generally associated with an original model that is used to build subsequent versions, while "flagship" refers to a leading or primary product, typically in a brand or company context, showing prominence rather than embodying an ideal standard. Therefore, "paragon" is the most appropriate choice for conveying a model of excellence.