The front and reverse sides of the same card are shown here.  The card was purchased by the present owner early in 2004 from an eBay auction, and the notes discovered only upon receipt of the card.  Trinity House have no records relating to the 1958 incident, nor of any subsequent survey. However, on page 73 of the excellent book "Crossed Flags," reference is made to the RANGITIKI being "briefly grounded on the Goodwin Sands, bound London to Lyttleton, but refloated" to continue her voyage.  One up to the postcard! 
2 October 2004 ~ Two up to the postcard!!  The Goodwin Sands incident is further confirmed in the section which discusses the Rangitata and Rangitiki in the book "The Ships That Serve New Zealand" by I.G. Stewart, some detail being given of the circumstances.  Finally, the information inscribed on the postcard is matched event for event in the book "Merchant Fleets" by Duncan Hawes.
Single click on the reverse will take you to a larger, more legible view.