Interesting find!! This CSIRO Drift Card was found in December by Liz McGuire at Ellenbrook Beach in Western Australia as part of the Australian Marine Debris Initiative monthly monitoring marine debris program. After contacting CSIRO they told us that this card was released at 33°17′ south, 115°03′ east, about 26 kilometres north of Cape Naturaliste on WA’s south west coast on the 27th March 1976. It was one of 50 released at this point. Their records show that only 6 had been returned before this one. This type of Drift Card had been used in Tasmania, NSW and WA since the 1950s and originally offered a 30c reward for those returned to CSIRO. By the 1970s this reward had increased to 70c which is the offer for the card that was found in Ellensbrook! Might just pay for the postage to send it back to CSIRO these days!
The release was part of a science voyage carried out on the RV Sprightly as part of a study on the movement of crayfish spawn. That means that this plastic card has been out there somewhere for 36 years. Just confirms that plastics even this thin are extremely persistent in our environment.