I would describe your cat as a seal point domestic longhair. Most cats are not any particular breed, and are not mixes of breeds, unlike dogs. That doesn't make them any less handsome or special, however! Domestic longhairs are great cats.
The recessive colorpoint gene, responsible for pointed coloring, originally came from the Siamese breed about 70 years ago. At this time, the colorpoint gene is extremely widespread in the domestic cat gene pool, so pointed coloring doesn't necessarily indicate that a cat is closely related to any specific breed such as Siamese, Ragdoll or Balinese. However, many people still describe all pointed cats as "Siamese" or "Siamese mix," so it's possible that's why he was described that way.