This Geocache is a letterbox hybrid cache and has been hidden to complement the series:
A letterbox for each Postcode and/or Suburb.
The second letterbox on the Yorke Peninsula after Dazzatron's GC3QFEN (unless there's an archived one I don't know about)
The cache contains a stamp for Letterboxers to use in their Letterboxing book.
Please do not take the letterbox stamp, this is not a tradable item.
No puzzle solving is required, the cache is at the given coordinates.