Good thing your going to the vet, it could be anything: Could be ringworm or it could be mites acting up that are normally on dogs depending on stress and such they act up sometimes, if they are they aren't contagious, if it's the mites that cause mange then they are contagious, and if it's ringworm be careful also. I don't know what a 5 pence is and what it looks like so this is my guess. Some allergies or fleas also get dogs to bite at fur and cause bald spots. Let us know what vet says will you..