Small brooches like this one, often in stylised animal forms, were worn by both Roman soldiers and subjects across the empire. They served both a decorative and practical function, being used to fasten articles of clothing, particularly cloaks. Archaeological evidence suggests that the centres of Roman brooch production were in the provinces of Britannia and Gaul. The hound was a popular symbol for the Romano-Celtic culture and it was thought that Roman soldiers when stationed in the British providences would wear these type of hound pins.
For more information on Roman animal symbolism, please see our blog post: Animal Symbolism in Roman Art.